The short answer: I very much doubt it.
The long answer:
A solid custom BoP for EVERY GR.3 car needs to be cultivated in the right way across multiple seasons of multiple series events. Despite what's been said by others, it's only impossible if you don't want to put in the time for it but the time investment requires for the initial R&D is a massive time sink.
It's usually better off sticking with either the PD BoP (because guys are paid to make those checks and balances for official championships) or cultivating a small selection of cars, preferably within the same drivetrain, for whatever series you plan to run.
So as a direct example, I custom made a BoP in GR.3 for GT3 spec of ~500 bhp and ~1300 kg as a baseline for an endurance series, but chose FR and MR cars to run in the series. Weights and powers were adjusted according to the pace, longevity and efficiency of the cars on fuel and tyre modifiers I was using, but quickly became apparent that the MRs suffered despite a 1-lap pace initially being ok.
Now, to evolve my concept I am doing a split in the 2nd season of my series where I split the drivetrains up, add one or two more to each and have one drivetrain as my endurance series and the other as a sprint series with exactly the same tracks, in order to execute a two-fold plan to balance the drivetrains on pace in their own self-contained environments to then reintegrate them into a bigger 3rd season later on.
As stated, this is a time sink, and any physics updates can mess with this in a big way. Whether you have tuning allowed or not also affects the cars differently because the performance potential is different for each car.
