Keeping in mind that these abilities are at risk of being stacked with multiple copies to a team, the following are commonly-brought-up ability concepts which are not in the game as of this post:
VERY slow moving area denial in a straight line - think Symmetra’s alternate-click from Overwatch. This becomes effective in choke points, but is outclassed by many current explosives, so may be unnecessary
Single-target powerful healing within line-of-sight (or out) - i.e. Healing beam/sniper (inverse sparks). I struggle with the balancing of this. It encourages single-target healing, but by definition means that unskilled players will focus only on their highest-skilled teammate
Barrier 1 - both teams can pass through the wall freely, but both teams also have hit scan weapons halted by the barrier. The barrier would have to be limited in both its duration and maximum HP. Explosives and throw-able projectiles may interact oddly with it, so would need testing.
Barrier 2 - Someone suggested a cloaking-style wall to hide evidence of a team’s location. (It seemed cute: like holding up a picture of an empty room while hiding behind it)
Muffler - canceling noise within an area is quite effective, but only when used with teammates. On its own, this concept seems underdeveloped.
Dual wield - Do your math. Consider burst potential of the high-power revolvers via head shots in your calculations. 2 pistols shouldn’t out-do a sniper rifle.
Unique movement abilities/gliding/unique parkour - Allowing a merc to get into places others can’t creates various problems in the design of existing maps.
Hud removal - I dislike this idea, as knowing one’s ammo and health are core aspects to playing the game effectively. This may also interact oddly with a custom HUD
Deployable spotter/nuller - Phantom already does this when a load out has bomb squad as an augment. For balance, perhaps it should be spread that an entire team can see the disabled deployables just like the bomb squad phantom. - Some have also requested it be throw-able to make it easier for breaching.
Shield (stationary or carry-able) - While turtle’s cute lil’ shield may or may not be in the works, The temporary modification of a map can be very effective while on defense. This same ability is difficult to apply on offense if it is not throw-able, however. Would require testing.
Drones/R.C. cars/objective-completing deployables - Please never implement this. As someone who came from Loadout where people sat in spawn and sent insta-gib hand-guided rockets out of their spawn, I dislike anything which can be used with no risk to its owner to such an extent. This is made more apparent when I consider that some people believe that having a character who can repair or defuse at range wouldn’t be a required pick 100 percent of the time on every map. Breaking core game mechanics in such a way seems unwise as well as a slippery slope. The character would either be useless or game breaking.
Slowing effects on bullets or deployables - These sorts of abilities strongly impact the lightweight mercs, but impact the higher HP mercs. I’m uncertain how this would be balanced between characters: slowing by percentage vs a flat numerical value, for example.
Flammable trail/flare – This skill set allows for annoying poke damage at first, but also acts as a super-strong stoker-type area denial after an area has been under a team’s control for a short time. It de-values stoker, even if the concept overall is cute.
2 part mercs - one requiring the other on a team - This design only is effective where teams are able to communicate effectively. In public games, this type of character is either useless due to miscommunication or a lack of their other half, or overpowered due to the lack of communication on the enemy team needed to kill the pairing.
Speed boosting - Boost pads increase the danger of screwing up spawn times while at the same time reduce the built-in weaknesses of heavier damage-focused players. For the already-fast characters, they become even harder to hit. I’m not sure where the win-win in this ability is.
Teleporting teammates - This messes with spawn wave timings. I’m unsure if the developer is prepared to balance around the existence of this ability. Because DB has spawn waves, this character could be VERY powerful or useless. There’s also the real risk of finding someone who finds it ‘funny’ to teleport teammates back to the first spawn when on the last point.
Knock back/pull-in/stuns - (AOE attract or repulse) - Moving enemies around via knockback is a game mechanic which tends to irk people the wrong way. When you play a shooter, being shoved around creates a feeling of helplessness. This ability can be balanced, but also is based on the map it’s being used on. For stuns, no one likes being completely unable to do anything about dying. Let’s avoid that.
Revive prevention – Please just let medics do their job? They can’t do much damage, so let them be effective at what they were designed to do. Creating a dead zone also ruins sparks as a character.
Deployable MG - Do you really want that choke point to be even HARDER to get through? This ability alone can lock down a hallway or side path. IF this is allowed, it seems it would fall under fire support just due to the damage that could be done to generators or the EV.
Umbrella-type denial to fire support mercs/dome shield - This combats all fire support mercs currently minus stoker. Given the system of how DB limits character selection, the merc idea makes me uncomfortable. I’d like to avoid any hard-counters (red-eye vs phantom for example)
Long-range insta-gib (railgun/laser) - OGOD no, please! - Jokes aside, having any insta-kill (non headshot) which doesn’t have a laser-sight attached seems a poor idea. If the ability has to be charged while stationary, it at least gives an enemy time to respond. The danger is that somehow, there will be a loop hole or lack of options for an enemy fighting this weapon.
Long-term single-target spotting - This is very effective, but also hinders the fun of a specific target for the duration of the spotting. I’m not 100 percent opposed to this ability being used, having seen it done well enough in Paladins, I’d be open to seeing it tested.
Disguising as enemies - In theory, this works fine, but with communication, the ability effectiveness quickly dwindles off: especially since you can now see at the top of your HUD which teammates are alive or dead (along with their location and name by holding z.) - Spy is considered one of the weakest classes in competitive for this reason, even if he’s very hard to fight in public games for some players.
Ability disabling - The idea that someone could take away Sparks’s revivr or a medic’s revive paddles is concerning to me, as the ability to heal and revive is what balances out their lack of firepower otherwise.
Heal nade/thrown pulse - Phoenix already has a pulse. Giving it to someone else as a ranged ability may decrease this medic’s use unless their loadouts are very different
Damage boost (AOE or single target) - Boosting a shotgun-user’s damage is spooky. Boosting a sniper’s damage is terrifying. Boosting a Fragger’s LMG damage wins you the game.
Helicopter area denial - So it’s like Kira combined with stoker, but it can’t be put out by smoke… Seems iffy.
AOE resurrection around a nade or deployable - This sort of steps on the toes of Sparks and/or Aura.
Armor packs - If used, the team will have to consider if this is treated as additional health, percentage damage reduction to a number cap total, or some other measurement. Each method of calculation changes the effectiveness on the armor based on the base health of the character OR the damage and rate of fire of a weapon being used against the armor. - It is unclear whether or not head shots would be reduced via armor, as each limb/torso/head hit box can calculate damage differently from what i’ve seen.
Jamming/forcing or preventing reloads - This seems irritating to deal with, as removing an enemy’s ability to use their weapon in some un-blockable way is a bit cheap and hard to combat. In this game, if you’re forced to re-load in a firefight, there’s a good chance you either have to retreat or end up dead.
Air drop - Not all maps are appropriate when planning a crate to fall out of the sky. The crate also may interact oddly with objectives such as the EV, generators, or plant points/c4. Hit boxes aside, I’m confused as to what would be received through this deployment method.
Timed detonation pack - Effectively creating a strict timed secondary objective out of nowhere, effectively creating a manually placed c4 with a need to vacate the area just before detonation (or require a defuse) seems a tad bit strong in large numbers, but with class limits, becomes a viable ability. The issue comes when many are placed in sequential order to detonate VERY regularly with no team damage…
Holograms/decoy - While the idea seems cute, I’ve never seen it done in an effective way when there’s any sort of tell to the decoy. This ability is useful against disorganized teams or inattentive members in most situations. Against more structured or vocal teams, the usefulness drops off quickly. I’d advise testing the concept a bit in DB just as a proof of concept.
Damage over time - As DB does not have health packs scattered throughout a map, preventing damage over time is very hard due to a reliance on medics. The damage could either be done by percentage or a flat rate, but the first one means it’s more useful against higher health mercs. The other argument I’ve seen is “If I had just used normal bullets, there wouldn’t be room for them to fight back.”
Prevention of non-natural healing - This flies in the face of the entire medic class. If a single character can lock out 1/4th of the character roster, then there’s a good chance it will be considered a must-pick.
Bow type weapon - Hit boxes in many game engines are VERY generous when compared to hit scan weapons. Furthermore, the speed of the weapon and damage have to be better than rifles but not reward a player with insta-kills for spamming the weapon towards a choke point if the weapon is to considered skill-based.
If I cared more, I’d capitalize and correct my grammar and spelling.
Give any general ability concepts that I missed, below.