i would scrap any integrated form of model scheduling other than just simple text
models do not follow schedules, they will jump all over the place and have no commitment to anything unless they're making $ and even then they work when they want
the chat piece (and #2) would probably take the longest but honestly that is most likely just going to be a flash frontend for a pretty standard core set of functionality (stream video, show text, record duration, join / part rooms)...
the billing api is straight forward if you have a solid gateway
fraud control should be a huge concern - check out maxmind.com, they offer a 'risk' assessment of users based on region, browser settings, proxies, etc.. saved us quite a bit
use flash media server and install it on a windows machine - my experience showed that linux was not stable at all with their product... maybe they've fixed that but it was not stable at all until we moved to windows oddly enough
anyway, good luck to ya!