Some "Pilot maintenance" is already allowed for Light Aircraft - however, you don't state what sort of aircraft you have or are thinking of getting.
Piston, under 5700 kg.
If your aircraft is used under an AOC work MUST be carried out by a Part 145 MRO / Employee
Oops. I guess getting a Part 145 approval is too much of an undertaking. Or is it?
The design of new modifications or equipment MUST be backed up by a Part 21 Design Organisation or OEM - this is NOT a maintenance task.
I am not talking of design or equipment modification, merely installing e.g. additional navigation equipment, or replacing existing types with newer equivalents. Does this fall under maintenance or not?