N classes need an overhaul. Theres only maybe two or three cars at most that can get within two seconds of the best time for N400 Nations race.
The N Classes are a different beast entirely. I don't believe it's even feasible to properly BoP the N Classes because of their very nature. To me, it's like when people used to run lobbies with power and weight limits. I hated those rooms. They were, by far, the most imbalanced rooms every time.
If PP was brought back to some degree, I think that would help the N Classes. I'm thinking of a BoP/PP Hybrid.
As for the list
@JayOTT provided, the only comment I would make is that I wouldn't put any car on a diet below 100%. Since the inception of this game, weight has been the best place to gain or decrease performance. I firmly believe that a 10% weight reduction would make any car over powered.
As for the tire degradation, I think the degradation model is simply too game like. It makes no sense. I have never known tires to degrade in performance in a linear fashion. I've never gone out on new tires, only to have them be worse on the next lap, then worse, still, etc, etc, etc. Yes, ultra soft qualifier type tires will degrade SUPER fast, but everything else isn't useless at half it's life.
I went looking for lap times and then I remember that motogp gives you all this post race. Here is a link to the last Malaysian GP lap analysis.
http://resources.motogp.com/files/results/2018/MAL/MotoGP/RAC/analysisbylap.pdf?v1_9d5960ba
Throughout the race, the lap times fluctuate, but they don't decrease by massive amounts. There's no tire changes in motogp, so these are the tires from new on lap 1 to toast on lap 20. The times don't just fall off a cliff. I realize that's not the case for all tires, IIRC, a few years back, the F1 tires would fall off a cliff after a couple laps, and then came back, but still, they didn't become useless at half life.
Asking to change the model is a bit too much of a request IMHO. It would never happen. But asking for a change in how much performance is lost seems reasonable.