This is excellent and detailed feedback. This is exactly what I like to see. Thank you very much!
You make a lot of very good points. I think all I can really add is that the flight model demo is (somewhat intentionally) made up of extremes. The MiG-21 is not supposed to be easy to fly, and the Jaguar is very underpowered which puts a big focus on what the aerodynamics mean for it. If the F-20 ever made it into the new flight model, it would probably fly somewhat like the older style planes simply because it has so much thrust and lift. I wonder if people would have said, "Just make all the planes like the F-20!"
As I continue working on the game, I'm coming to the conclusion that I probably want to shoot for some middle ground between the two. As of right now, the flight model is currently an expanded version of what was in this demo, but with more fidelity in the control systems. E.g. you have manual control of flaps and the nozzle because they are actual control surfaces versus magic abstracted things as in the demo. I think these are good things to have and I'll definitely be keeping them. However I'll probably tune the flight model such that they are easier to fly, but still driven by this physics system.
There is also a possibility (no promises!), that a toggleable "simplified flight model" could be in the game, but that remains to be seen pending work I plan on doing this month.
Another thing I've come to notice, between comments here and the YouTube videos that get posted, is that I (foolishly, honestly) under-estimated how much people would fly with the mouse. From the very beginning, I begrudgingly included the mouse flight only as a concession for people without joysticks. I never liked it because by its very nature it will mask many of the interesting properties that you get from flying manually such as a lack of stability, wind, turbulence, and many such things. It also lacks nuance and is prone to "throwing the joystick around" as if it was an arcade game. As I've watched people play and report their findings, it seems like the vast majority of people don't even consider playing with anything else. So many people praise the old flight model, despite it's 100% broken and placeholder status, as "realistic" and good. It's hard not to wonder why I should even bother.
Between all of that, I absolutely 100% need to re-implement mouse controls before the next release. They're currently broken to the point where I've flat out removed them completely in favor of a simple virtual joystick because of the cockpit and new camera system. Honestly, I wasn't planning on re-adding them back any time soon, but with what I've seen recently it seems like suicide not to.