Owner maintenance is part of the Part F remit and as I see it the Part F company has first to make sure that the owner is able to carry out the 50 hour check to a satisfactory standard, they would then in effect issue the owner with a Company approval to do the 50 hour check or any other simple task that they see fit.
I thought it was the Part G organisation that could authorise an owner to do some maintenance tasks (stand to be corrected). However, this does bring into issue whether this work could be considered to be in a "controlled environment " and specifically what kind of work would be allowed. The last time I looked at this, it would be the responsibility of the owner/pilot (what about a group owned aircraft) to issue a CRS (release to service). So, how does the owner do the AD research etc.. and lots of other ifs & buts.
Some people believe that Part M is going to improve standards, improve their maintenance and reduce costs. I hate to disillusion them!