I hate the idea of franchises. You'd alienate a lot of fans, as you'd be moving teams to be nowhere near them, essentially because some counties are really bad at selling tickets to games.
Less teams also means less opportunities. We'd have young, talented players not playing T20, whilst some ageing Australian journeyman does instead. Look at teams like Leicestershire. They've produced the likes of Broad and Taylor in recent years, yet those players young players wouldn't get the chance to play T20, because there would be so few teams. And let's not forget that Australia franchised to create more teams, which is part of the reason for why it works so well.
This is what grates me with the likes of Buttler wanting it. He got his break in the Somerset T20 side and then got chances in other forms of the game. With a franchise, that wouldn't happen.
I think we do need some changes though. Bring back the condensed calendar in the middle of the summer. Perhaps spreading games over a 6 week period to try to get the best of both worlds. This would enable teams to sign big name overseas players, that can play the whole tournament.