I tried posting this on your blog weeks ago, but it seems my comment disappeared.
Anyway, I think I have a great idea for easy, seamless and universal mobile support. Instead of maintaining a list of user agents (which will always need to be updated and will almost never sync perfectly with mobile theme switchers), how about this:
Create a "don't use super cache" or "only use legacy cache" tag, which will force a page to not use super caching and only use classic caching. Create a mobile support setting in WP Super Cache which asks the user to specify their mobile theme or plug-in. Then simply get WP Super Cache to insert this tag into the mobile theme header.
This way, whenever the mobile theme is used, it will use legacy caching, not super caching. As the user's mobile switcher/plug-in is selecting the theme, you no longer need to specify user agents yourself, and it will always be up-to-date and perfectly synced with the user's chosen mobile theme.
Is there any reason this wouldn't work?