I would love to see some challenges, mini-games or something, in game or as a separate mode.
Regarding the warmup, some Baserace type of gameplay, build the defenses until the game begins?
The hardest part (for SD) would be to create some kind of The London sewage system underneath the maps where you could play TDM, obj or challenges, mini-games, etc. Not to fun, coz you will not want to leave the warmup 
3 vs 3 OBJ games are not very fun, any suggestions to fix that?
A 5v5/6v6 game is not fun when played with 3v3, my 1st reaction is “well duh”… saying people won’t join a low population server is nonsense, you’ve got no idea what type of server people will and won’t join and throwing that blanket statement around is just false. If SD are going with a server browser and match making, the MM system could fill those servers up easily. 6 people on a server, 6 looking for a random game via match making… boom, full server. I’ll be honest, I don’t see or expect SD to do anything to cater to a small volume of players while they wait for more people to join… seems like a waste of resource for something I believe to be a non-issue.
I still want some challenges and a training room, out of the game, played locally or co-op. You play the challenges and when your favorite server is populated you automatically join in :D. Something like the Auto Join a server from Steam TF2.
Granted there was no MM in ETQW but I felt the same there. Join an empty or low pop server and wait, there is only so many times that running around in warmup is entertaining or playing a low pop game, which I think we mostly all agree isn’t fun, before you simply just give up. We’re also seeing this in the Alpha, once a server reaches a critical point more often than not it fills to capacity, getting to that point is usually the hardest part though.
That being said, I agree it’s a lot of work (or just additional work) for a distraction. Perhaps better ways would be on the launcher/browser front end to ensure servers get filled with minimal waiting. I’m just a little cautious over relying on this purely because it needs a big enough userbase to work effectively.
Maybe what we need to agree on is that a server with <6 people on it is undesirable to join and could mean players go elsewhere for their fix. At least if we accept that as an issue SD will need to factor something into the design to counter such situations. ?
Well, as a simple remedy, I’d say that at least removing the spawn timers in low pop games can keep the game entertaining and action packed. If a server has 7 or fewer players, then make spawning happen immediately. Then once that 8th player joins, then kick the spawn timers back in.
No?
Rule of thumb… don’t dick about with the core game. Warm up mini-mode or something, sure why not, but don’t mess with the game due to player count, that’s a big no no.