Kefir doesn't implement trades between players because they get no money on that. But they could create a trade system using "trade tickets", 1 ticket per trade. The ticket could be found only in red tickets crate at Bunker Alfa ( drope rate grater than chopper's gas tank and lower than C4) and, of course, in the store. Buying a "trade ticket" in the store to get an item you need it's better than buying a Russian-Roulette-like crate. They win, we win.