Welcome to the forum AOS. Unfortunately your comment is not correct. Any person can perform maintenance on any experimental homebuilt aircraft because FAR 43 excludes experimental homebuilts.
You probably meant to say that only the builder can qualify for the limited repairman certificate to do the annual condition inspection. Only the condition inspection requires an A&P(or repairman). The maintenance, including major repairs or alterations can be performed by anyone.
In my experience, there doesn't seem to be much of a problem with owners performing preventive maintenance items listed under FAR 43 App A. on certified aircraft (where FAR 43 does apply). But FAR 43.3 does require that the owner or operator have a pilot certificate. I think this requirement for a pilot certificate insures some competency in the view of the FAA, because all pilots have to pass a written test which includes some limited questions about maintenance, engines etc.
I support this proposal to allow owner maintenance.