I was reading this forum for a long time but never post anything on it, for two reasons:
-my english is quite bad (I'm french)
-everything on xbmc dev roadmap is 99% perfect (using xbmc as end user is quite easy).
1% not perfect is about controlling xbmc in a complete home theater system.
a lot of stuff are in Development but nothing universal.
using a little touchscreen in dual screen mode or in http api mode will be the most universal we can use.
a simple remote design with traditional arrows, back, enter, menu key will be enough, nothing complicated.
we can find this kind of usb touchscreen for 100$
easy to use and not expensive.
I've no skill in Development unfortunately, may be someone with enough knowledge in xbmc dev is interesting ?