It would appear I am one of a very few (only one?) reading (or at least posting in) this thread who also is interested in customizing a WM5 SP device (i.e. non touchscreen)...
But just in case I am not :)
Finally run into something that makes a WM5 SP device closer to what I am looking to do with it:
http://www.sbsh.net/forums/index.php?showtopic=15747
For now I am using this OS X one:
http://www.jammasoft.tk/