I've never written a WebStart application, so I can't tell you the details right away, but since you speak about RCP and since OT/Equinox lets you write RCP applications with OT/J I expect this to work out fairly straight forward.
Do you have experience with RCP via WebStart?
You'll have to include all bundles from the org.eclipse.objectteams.otequinox feature in your application. Since you won't install using p2 you'll have to manually add a few lines to config.ini, that might be all.
If you have a RCP-via-WebStart Hello-World I'd be happy to help adding OT/Equinox to the stack.