Aviator1512
While you are quite correct that subpart F & G don't require different companys however the subparts have to maintain a "distance".
When this Part M first anounced and the CAA held a number of "roadshows" the direction was very much on the lines of two companies.
We decided to go along the two companies route (after the first roadshow) so that we could offer subpart G services to companies that might not want the subart G stuff and wanted to just get on with the subpart F business.
One of the expences of Part M was the ever moving goalposts, for example just as I had got all the stuff for the controled enviroment for my C152's they withdraw the requirment........... more useless work!
I see one of the problems for the maintenance business is the new system has resulted in a bit more transparency in charging as with the maintenance split between two companies the customer gets two bills and can see what he is paying for.
The CAA charges and audits these as two approvals and so one insted of two days so my time is given to this rather than paying work, this all adds up to more paperwork and cost.
Some above are very quick to charge the maintenance business with overcharging but cant see the level of investment in time and effort required to meet these new regulations, I only wish we could charge the same hourly rate as the CAA charge for engineering investigations, then we would be making the sort of money that Bose -x thinks we are!