Hi Steve,
Cynthia led an aD project some years ago for a donor service provider website, GivingCapital. They're still running at www.givingcapital.com, but they've moved away from the campaign/donation model to a private foundations model (so you can't see the donations subsite anymore). You might try contacting them to see if they're willing to release some of the donations source for ideas.
It was started with ACS 2.x, and slowly moved up to the level of ad_page_contract when that was out, so much of the code would be out-of-sync with OACS. But the workflow might be interesting. It had a campaign creation wizard, matching fund drives, white label (branded) templating, sub-accounting, etc. One of the things I saw 'missing' from your workflow is refunds. Important if you let users type in their own donation amounts, regardless of a confirmation page. There was also an alternate 2-click workflow for repeat donors.
Well, good luck...
