In airplane ownership the engine is actually probably the most discussed/thought about maintenance item. Sure you need to replace the brake pads, the oil needs replacement but, the engine, it’s very expensive and it does wear out. So, any maintenance model of airplanes most certainly needs to model engine wear.
I agree about the maintenance system updates of the OP. In real life, you wouldn’t check one subsystem. You would quickly check all the planes high wear but easily checked items at a low cost. Brakes, oil, etc, should be able to be checked with a single click and then fixed as a single click.
Maintenance schedules on planes are actually pretty standardadized and it would have been better if the system had followed that more in the game (obviously with significantly reduced hours).
Overall wear rate is ok but engine does seem to wear out too fast (although I wonder if that is also modelled based on how people use the engine).
BTW, hard landings will wear out your landing systems way faster. I did a hard landing and I went from 100% to 25% in one flight. However, normal soft landings only wear about maybe 5-10%.