This sort of thing was actually one of my secret possible future projects slightly after the time when I created /mystats and was toying around with uses for them. I think that in the right hands it could be a good idea, given that the "right hands" made extra sure to come up with achievements that promote good Tremulous gameplay and none that do not. However, most "good" behaviors are technically difficult/impossible to detect and recognize, where all the "bad" ones are like one line of code.
Like /mystats, I wouldn't ever do anything like this that extends beyond a single, local game. The logistics of doing things across servers and over time are just not worth it for something like this, plus all the hack/abuse issues people have mentioned.
Actually I began to work on this by investigating how I could possibly display them at the end of the game without modifying cgame/ui, which took me to trying to figure out how to make a pre-intermission to display them in CP. This pre-intermission fake intermission time is what led me to rewrite Ben's !pause idea.
So yeah, I don't think it's actually feasible to do in Tremulous in a way that would promote good gameplay, but my toying with it did bring us !pause, so something good came of it.
