rock on! wow, very on par with my own life dreams...
that said, no i haven't done it yet but to get this thread moving and to brainstorm/communicate:
1)i have stayed with people who live in buses, and who toured in their mobile living spaces and it seems extra insulation is rarely used. i think the reason being it takes up too much space, and when in such a small space you are not going to need a big heater to keep toasty in the most damp and chill climates (excluding the "don't go out or you will die...really!" winters).
2)other than just RVs and busses I have seen pretty well down trucks with large loft extensions over the cab, and lots of fancy woodwork adjustments (think gypsy-style)
3)showers inside i have not seen...what about something you could rig up outside the bus?
a couple suggested links:
http://www.lafilmmakers.orghttp://www.mrsharkey.com/busbarn/busbarn.htmbest of luck!!!