Create a website-building app, in Arc, which will:
1. give tips on-the-fly (i.e. while the user is building it) for properly writing for the web, as per useit.com
2. automatically include a decent search engine
3. make it easy to modify pages
4. include history for page changes (visible only to the website builders I suppose)
5. include an archive for older pages (i.e. for events etc.)
6. make it easy to link to other pages on the website, including back links (i.e. if a new page is related to an older, existing page, you can specify a back link on the new page which creates a link from the older page to the new page)
7. ???
8. Profit
P.S. When I said website-building, no, not a blog or programmer-oriented site: I mean a business site, one which doesn't suck like all the other b2b/b2c sites.