So I've been thinking of some real suggestions on crowded servers and gameplay in general, but I come mainly with inventory issues:
- I bought like 6 sg 552 and 6 vests, then left them at the stash for using them later; when I'm taking 1 sg only i have no problem: LMB on it and you directly take all those 6, 1 you carry, 5 to the backpack, then RMB on the backpack ones, which return to the stash.
The problem: i want to grab only 2 sgs from those 6: not possible, you can only take the whole pack (1 as first wep, 5 to the backpack). I'd suggest
1 click 1 item, just as the armory when you buy, and
ctrl + click for all the similar items. That, or viewing the items you have at your backpack and at your stash 1 by 1.
i solved this by dropping 1 to the ground actually, and grabbing only 1 again, but that's a bit awkward and some pesky teamies might rob you all of a sudden

- When you carry no grenades with you and you walk over 1, you have to tap f instead of picking it up directly; i can't tell if that happens because you only pick the kind of grenade you last had. I know that's kinda more realistic, but don't know if that's how it should be or not.
- Persistent special weapons: when you get killed having a special weapon, one bought at the armory, it usually disappears. Sometimes this happens also with a special weapon you took from an enemy: I heard a guy shooting an ak74, I killed him, but he dropped no weapon at all.

Don't play with me DocStone! It's okay that special weapons bought at the armory don't always appear when you die, you can always buy a new one if you have RP, but not those sweet hidden ones.
On massive coop servers: I can't really make a suggestion, just saying that sometimes it's way too hard to destroy their comms or complete side missions: literally 40 enemies at 1 area. But I actually love that...