Instead of a 3-wins match, how about a "best of" match arrangement?

You can have varying lengths according to the type of game. For example, in checkers, a longer match is usually required to determine a victor. 24 to 40 game matches are typical at the World Championship level, but this is a bit much for online play. Perhaps 13 games would suffice. Whoever has the most points wins the match.

If it ever reaches a point where it is mathematically impossible for the other side to win, then it can be stopped.

For exmaple, if there are 4 wins and 6 draws in a 13 game match, the last 3 games need not be played since if the winner lost all 3 then he would still win.

This is actually what they do in checkers. Since Alex Moiseyev was up 8-2 over Ron King in the last World Checkers Championship, that match was called off early.

Chess would need fewer games, maybe 7.

Gothic Chess would probably only need 5.

Again, the same rules apply. If a mathematical certainty has been reached, like 3-0 in Gothic or 4-0 in chess, the match can be stopped.

I think in drawish games, you should rate the result 1-0 (like checkers). In other games, you should rate each game as they complete.

Just an opinion, but I think the reasoning makes sense.