Raven
All this you plan is possibe (and some more
).
Get a BU0836A from Leo Bodnar - the version Bu0836X come with some easy conectors but cost about twice and have the same functions, since this kind of project require solder at all, I prefer the basic version.
A bit cheap alternative for USB controller with same functions (shipping include):
http://simrace.hgsitebuilder.com/circuits
For trim get multiturn potentiomers or encoder.
For switchs you can use toggle (lever) type, lever momentary and momentary push button.
Find cheap in eBay from Hong Kong.
Basic requirements: know how do solder, know how differentiate + and -
and some DIY skill.
Sample:
http://www.escuadron69.net/v20/foro/...affe-v2/page-1
Sokol1