it may be more advantageous for the aircraft owner to get his/her own Part 66 license...
Or an FAA A&P/IA.
Without a doubt, the only way to really cut into aircraft operating costs is to be an authorised engineer and do your own maintenance. I knew a few people that do that.
One thing which keeps tabs on this practice is the scarcity of hangars in which maintenance is allowed by the freeholder.