O.k. but those physics and the flight model can certainly also be adapted to 1.15.4.
The thing that makes 1.16.0 complex is the use of DX9, that is also the reason why many things in the cockpit aren't working anymore (e.g. analoge gauges and engine bars in the havoc) and there is no way to fix this without real good coding experience.
Most of those code gurus that made the complex coding for EECH-Allmods back those days, sadly aren't interrested anymore in EECH or simply have no time to work on it again.
That's why I think, lets stay with 1.15.4 and make some new things, like more details for the terrain (trees, buildings etc.), maybe another new helicopter or something else.