I must confess this stuff goes way above my head. I went to a presentation on Part M a while ago and it went over my head then too. Reading about it now, and having spoken to a few maintenance firms recently, it is obvious that interpretations of the regs vary so widely it is a bit of a joke at times.
The one thing I do understand however is airfield / maintenance politics. Whatever system is adopted it needs to be realistic. Currently, many (many) owners do not use the company based on the airfield for various reasons. It might be no good, or it might be OK but you cannot give them any work (other than trivial) in case there is a dispute in which case you will have trashed the one band which can give you a release to service signature in an AOG situation.
My experience is that the happiest owners who keep their planes in the best condition are ones who have the freedom to pick and choose who does what (and yes a disproportionate % of those are N-reg because doing exactly that is easier on the N-reg). I am one of these but it took a while to suss things out.
Large chunks of the maintenance scene are nothing short of a disaster, but if you are not careful you will end up over the barrel belonging to one of these companies.