A refreshing exception to this is the Experimental Amateur-Built (EAB) category, basically home-built aircraft. Subject to a different set of regulations, the owner or pilot of an EAB category airplane has surprisingly wide latitude to install equipment, perform maintenance, experiment with the power plant, and so on. I can't so much as run a USB charger out to the panel of a Cessna 172, but I can make major engine and airframe modifications to an EAB airplane and do the annual condition inspection if I was the builder.
Consequently, a lot of the innovation that's happening in General Aviation, including avionics, safety systems, ignition and fuel systems, is happening in the EAB world, with the Certified world catching up later.
With pretty onerous restrictions on how fast the plane can go, how powerful the engine can be, and once sold, a lot of those restrictions on Certified aircraft apply to you as the new owner.
Everything that you just said is incorrect, at least in the USA, where the overwhelming majority of all E-AB aircraft are built and operated.
There are no airspeed restrictions on experimental amateur built aircraft, other than the 250kt limit under 10,000 feet that applies to all aircraft.
There is absolutely no restriction on engine power output for E-AB aircraft.
The only significant restriction for the second owner of an experimental amateur built aircraft is that they cannot get a repairman’s certificate for the aircraft. This means they will have to hire a licensed A&P mechanic to perform the annual condition inspection. Other than that they can still maintain or modify the aircraft exactly as the original builder could.
I refer you to FAA advisory circular AC 20-27G for further info.
Consequently, a lot of the innovation that's happening in General Aviation, including avionics, safety systems, ignition and fuel systems, is happening in the EAB world, with the Certified world catching up later.