I've had the idea to utilize XBMC as the main Pandora interface for several years now.
I have some (partial) plugins lying around which implement the following functionality:
A .desktop file scanner which can launch PNDs and other apps (works in most cases)
A port of pndstore (segfaults, haven't bothered to look into it).
A rom manager and emulator launcher (there is a standard plugin for that which needs only minor tweaks)
A port of several configuration utilities such as my Nub and TV-out configuration tools (needs to be done, mostly some GUI work)
The main problem is that the current port of XBMC is buggy as hell (prone to crash, audio/video work poorly) and it consumes quite a bit of resources.
Naturally, additional stuff would need to be added as well such as e.g. a lightweight 800x480 Pandora specific skin with some branding and this sort of stuff.