First, I think this is a great idea for a game, and a great time for it to come out in the boooring offseason. Thanks Hugo Koblet.
As far as the contest itself goes, I think it makes sense not to have any cutoff or exceptions, for the sake of simplicity. The same pool of riders should be available to everyone, and it's up to those people to decide whether some gambles are worth it or not (ie. if Pellizotti, for example, ends up suspended then you risk wasting that spot). If people miss out on 'slam dunk' bargain picks, be they injured riders, returning dopers, etc, then that's their own flaw in picking their teams.
For numbers, obviously if you could choose riders with 0 points last year there should be an upper limit of how many you can choose. The suggestion of 25-30 seems to work fine, as that's protour levels of restriction. Those who have already chosen a team over 30 have 3 weeks to figure out which couple of riders to drop so it shouldn't be a big deal. Either way, clear rules soon would be great for us all.
That's my 2 cents. Thanks again.