We're just completing our Subpart G and F approvals and have been warned about this. The situation already existed for JAR145 companies.
I've had to change my Subpart G CAME from 'Piper Single Engines' to individual models (not even 'PA28 Series') due to different engines (PA28-140, 180, 151, 161, 181, 201 etc etc)
We are still up against a very unlevel playing field with some companies already holding Subpart G approvals for 60+ aircraft types (and a type on one company's list is 'PA28 Series'...!). Bet they really hold up to date maintenance data for all those types that we're being told we now have to have if we want the type on our approval. I've been assured things will change at their next audit.
Still far too much individual CAA airworthiness surveyor interpretation of the rules coming into it.