I have an idea to solve every issue we have on parts and engines, why not limit the amount of engine changes to 3 each season, but retain the 10 engine parts available? The complexity of the new engines will ensure this is all used up. If they don't manage this, they would have a fine of 5% of their balance. I will separate them into the ICE, TC, MGU-H, ES and CE. No MGU-K as they will be removed soon in real life.
For parts, limit it to 3-5, but retain the amount of parts. You can make parts more complex so this is used. Again, fine of 5% of their balance. I will separate the parts into suspension, brakes, gearbox, front wing and rear wing.
Also, the parts should wear more slowly for this to work, maybe only a bit slower, but slower please