Most of the essential points have been stated already.
Type conversion, differences training, refresher training etc. can all be carried out un-remunerated or "expenses only" on group owned permit aircraft. The PFA coaching scheme is an example of this where the training is done by FIs or CRIs (SEP).
There seems to be little scope to use the aircraft to generate revenue other than display flying.
I gather previous attempts at commercial operation with a foreign CofA (Hungarian?) ran into difficulties. I'm sure the likes of Jeffries and Goode will know the ins and outs, but it doesn't look promising.