Okay, I made a theme switching plugin.
The rationale for it was not that I wanted to let my users pick between different style, but that a) I wanted to offer a "lite" version of my site, without the wordpress/buddypress shell around it, and b) maybe one day I or someone else can make a mobile theme, and so this plugin has an option to send users on mobile to an alternative theme instead.
- theme selection in user profile
- toggle on/off via admin/plugins
- default theme selection in admin/plugins
- optional mobile theme selection in admin/plugins
As with other plugins, this is quite a hack; I've already submitted five ideas for 1.5, but I'm betting this would be something likely to get included in the core at some stage. Any thoughts? Or feedback at least - bug reports would be great :)
Plugin is here: