It's already done, you can check players status before joining (game settings icon)
Btw, speed depends only on the players, but fast games is (usually) only with settings:
timer running for a few hours, better not nonstop 24 h/ day (if you play with peoples from other time zones)
1 hour per player + 5 min per move -> it should be live game.
1 hour + 15 min (working for example between 8:00 and 16:00 o'clock -> it can be 'live' or also fast turn-based game, even for 2 or 3 days.
If you want fast games, joining to play with timer 6 hours, or 1-3 days doesn't make sense at all.