I know that I'm a freemium, so I'm the last to say anyting about speed games, but:
If you check out the speed games that been played in freestyle you'll see that 99% of the game is waiting till the clock goes down so you'll be the last to make the move (the only players that don't play like that in speed freestyles new freestylers and new recruits, which being farmed by experienced freestylers, usually with CM), so I think in freestyle the best option will be to even lower the time to 1 min. which should shorten the game (which is the interest of freestylers), and bring it to be even more exiting.
You aren't kicked right away, but only after 3 straight missed turns... which in sequential will take the least of 16 min. (in game of only two players) if not longer.
My personal idea is that if the time will be longer to take a turn, you'll be able to play more sequential games at the same time, but it will also make games longer (think about it: a simple 2 man game that finishes in the 5 round, can take two and a half hours), not everybody can stay online for that long, and what you'll get is that people that have all day long will just drag their turns and win games because every other player has to go away eventually, you can also call it a new farming system... (3 players game that only one player is stalling will go into 6 round at best after hour and a half, now think what will happen when there are more players involved and that most of the games go beyond 6th round).
If you bring the time for turn down, you wont be able to play multiple games at the same time, but you'll finish much more games in lesser time (2 players game, that are the common speed game, will be over in ten min. top), while you totally focused on that game (which is really difficult to do with 3 or more speed games at the same time).
P.S I played some speed games on halloween (again, THANK you for that CC) so I'm talking out of (some) experience