vee-tail-1 you are so so wrong!
To have a part G company issue an ARC you have to stay within the "controled enviroment" of that Part G company. Yes you can change the company that maintains the aircraft but not the part G company that supervises that maintenance.
Once you step outside the "controled enviroment" the CAA fees will cost you dear.
As to the list of things that you can do these have to be approved by your maintenance company and they have to check that you are able to do these tasks, in effect they will have to issue with a "simple & limmited" approval as part of that maintenance company to carry out these tasks.