I got asked by a team of first timers who have never done any professional coding or design if I wanted to chip in on a competitive MMOFPS they want to make.

That’s not going to happen. Between the rise of cheating, the insane hardware and optimization requirements of an MMOFPS, the general lack of interest in the genre (most have died due to low player counts), and the sheer amount of time and effort involved in designing and balancing the game even after it’s largely feature complete? Forget it, I’m better off buying lottery tickets than hoping for anything to come of that.