JScott, I'm sure you know from your background more than you realize. Think of the tools you like to have as an affiliate, and the things you like/dislike about the programs you promote. Which we both know you have a healthy list of
. Hash it all out and form a plan, the rest should fall into place as far as hosting and such.
One of the biggest "mistakes" that I think people make is they launch their program with just a CCBill account or something then make the switch to NATS/MPA etc later on. If you think you will use the Cascading/xsells/webmasters tools etc, then you should just get setup now and not a few months down the line.
Hit me up on icq if you want to chat.