"...this would become very much like the live chess option."
It would become so much like the Live Chess option that it's not even worth considering. We already have live chess. Since one would not have to log in to Live Chess section to play fast games, two things would happen:
1. People who enjoy slow games would have a hard time finding a game, as the main site would be completely over-run with Live Chess players.
2. The Live Chess portion of the site would die off.
Chess.com would be a worse place. It'd likely lose many members and become another Yahoo!.
I do like the idea for tournaments to have a 'vacation = loss' option.
The "something else" is a "fast" (5 minute or so) time control in "turn-based" chess. Because leaving the computer (for more than just a minute) would cost you the match, this would become very much like the live chess option. The mean average time per move would probably be under 3 minutes, meaning that the first 40 moves (if it gets that far) would take no more than a couple hours. A good option for those who can be sure of the next three hours or so at the computer.
If this were implemented, it would probably be good to allow players to adjourn by agreement or (probably easier to implement) adjust the time per move up by agreement. It would also be necessary to disable vacation for these games.
That's the original thing, and it's a solid idea for an entirely separate reason: Allow an option for a "vacation=loss" (and "timeout=loss" overriding the preference for not winning after timeout) game option. The separate reason is to allow tournaments to be more timely. If a tournament is set for all games being "vacation=loss," then it will be able to go faster. And people who wouldn't like to lose by timeout and who can't commit to meeting the time controls can find other games or tournaments.