There are bigger and heavier permit aircrafts but they tend to have quite a price tag attached to them.
The price tag, as eni fule kno, is just the start. !
There are plenty of eye-watering examples ,in posts here and on "the other Forum" , where horrendous costs are forced on the owner.....don't like it? tough cheese! no release unless you pay the "ransom fee"
Permit costs are a fraction of Cert. costs.
Regarding "doing your own work".......Ever tried asking the local garage if you can use their workshop to maintain your car?....yes! it's been tried , multiple times....everything from a communally owned workshop, to weekend/evening use of a main stealer's, with a professional mechanic on duty,to assist if you run out of skill or aptitude or time!....workshop HAD to be clear for normal business.
Hire-costs worked out about half their normal chargeout- rates.
Now, translate to your local aircraft maintainer. A pal of mine was a pilot(PPL) mechanic and auto-electrician. he had use of a Permit A/C and a 172 and 152...much maintenance was done by him and signed -off by the resident engineer....he also repaired starters, dynamos and Alternators, for the engineers' customers........The thing being, he'd built a relationship with that "ticket -holder" who'd grown to know and trust his expertise and workmanship. Ultimately, the Engineer was responsible, he'd literally put his career in my mate's hands.....
For you, that would be a HUGE ask, I'd expect you to pay accordingly, so, I don't think you would get to anywhere near double the cost of running a Permit aircraft.....
INSURANCE!!! CHECK! I'd expect, with the huge cost of Cof A repairs, that would be another big hole in the budget.
If you can afford it and don't resent the huge extra cost, it's a no-brainer....get your 172, MAKE SURE THE SIDS HAVE BEEN COMPLIED WITH ...hedge your bets with a Rheims, which were corrosion-proofed ,new ,at the factory...... fly it and remember to hand over a blank cheque every time it wants fettling.
(maybe you hate maintaining your own, but I get the impression this is an important part of your flying fun)
look at 4-seat permit stuff!