Achievements
I personally prefer in game achievements, ala cod/titanfall challenges. It actually is not a big deal to me, but I think it is a good feature for a lot of people. I know some achievement whores that 100% every game. 100% on this game could lead to a lot of purchases since presumably you have achievements specific to each merc. And you can reward them for completing difficult achievements with xp, camos, xp boosts, etc…
Stat tracking
Sorta like battlelog I suppose or WoW armory. Let us look up other player stats on a website/mobile app. I think we’ve heard word on this already but just reminding it is important. It will be kinda weird though since players can change their name. I wonder if nexon has a static numerical identifier that can be used to find a player.
Spectator lobbies
Basically allow spectating in a lobby separate from the game being watched. This helps promote a social experience since you will be capable of chatting easily with other players in the lobby. The lobby will need more social functions than being in game to be worth having and the lobby could be on a time delay of like 30 seconds so competitive matches aren’t ghosted. Making partnerships with shoutcasters could allow them to stream their audio through the client, sorta like dota2 does.
These have all probably been brought up before, but I was bored 

