[QUOTE=k0k0nat;474229]Now its like:
“uhmm… yeah… I need a medic and FOPS for sure… maybe an engi because the other two classes dont seem to have any benefits for this objective”
I mean this is SO static. Why would I pick Sniper class now?
It was more fun with 5 different classes, even if u pick a “useless” class for the situation in-game it felt better.[/QUOTE]
I feel the same exactly, been running pretty much only variants of medic / fops / engie lineup since the patch came out 
Prior to that, my lineups always included at least one very situational (for me) merc: a sniper (and nearly all the time a second one: Nadder or any of the shotgun mercs). See I suck as a sniper, but I’ll never get any good at it unless I play with it once in a while when the situation is right and my team could really use one. But now that option is gone because I can’t afford to waste one of my 3 slots on a merc I might play 5% of the time…
I’ll make a parallel with TF2 again. When I started I played only about half the classes, wouldn’t touch Scout, Demo, Sniper and Spy as I was not comfortable with their mechanics. But because I still had access to all of them in game (and because I’m one of those idiots who puts the success of the team first), I would once in a while pick one of these when they were really needed and do my best with it. The result is that I can now play decently with any of them. I’ll be happy to let someone better take on the role, but if no one steps to the plate and the situation calls for it, I’ll do it and be able to contribute and have fun doing it.
Without the possibility to bring in your lineup a merc you are weaker with so you can train up on it if the situation is right, I’m afraid people will stick to the same mercs over and over. That make the game more repetitive and eventually boring. It’s also bad from a revenue point of view as there’s just so much you can spend on skins, custom guns and what-not for the 2-3 mercs you play all the time compared to the 10-15 you could be playing fairly regularly.
I don’t think you even have to have access to all your unlocked mercs for this to work, just enough slots so you can field a core of mercs you are comfortable with and then fill the rest with a couple to be used if the need arise or for the lolz (5-6 slots should do).