Ive been thinking about this alot too
Its something id like to do with a pro version of the printer, and with a camera watching so that it can do self calibration.
I was thinking we could just add 3 or more sets of galvos so that printing would be faster and we could set things into the print aria and print around them over hangs and all.

I haddent thought of using mirrors ... that is a good idea too!