I echo what other folks have said above.
It strikes me that you might have to be a bit of a salesman to your client: Tell them that using some sickly ISP will slow the project. I've hosted sites at (and been reasonably-pleased with) Rackspace since February 2000; having that much control over your environment is invaluable. You'll thank yourself when you're running into problems.
Also, this might be heresy in some circles, but you might want to take a look at Slash. I've never looked closely at the quality of the code (I've managed to change what I've wanted without problem), and it has a bad reputation for clarity, but it is a working system that you might want to borrow from. Remember that it's GPL'd.
-Declan (declan@well.com)
