100 projects with 1 client, or 100 projects with 10 --or 20 clients?

I'm still not convinced--despite the existence of a wikipedia entry--that this isn't a question of needing better overall management. And good project collaboration (something I have taught) might mean that you assign someone on the client side to be the keeper and indexer of the hundreds of emails. If you're really dealing with that much information you have to choose what you micromanage. ;^)

But as a management adviser I'm more concerned about your assertion that everything on your list is of equal importance. A colleague of mine is fond of reminding clients "Fast, Cheap, Good: Choose the two you prefer because you can't have them all." And I think this is important here: if you're actually price sensitive, then you shouldn't expect to get everything you want exactly as you want it. If price doesn't matter, why don't you find someone to design this ur-system for you? But then you might not meet the "I don't want to know about maintenance and installation" criterion.