[Hayate.RU[53]]

This mod allows having different buttons files. I.e. you specify which file will be used for your plane's FM.
As for usage... the developer writes the following:
In the airplane's class you should have a path to FM file as
Property.set(class1, "FlightModel", "FlightModels/Ki-84-Ia.fmd:game/gui/myfm");
Where myfm file is a file with FM for your plane (packed as usual for the buttons file).
Engine parameters can also be specified as above:
Engine0Family Nakajima:gui/game/myfm

So you can add the new plane as you would normally do, but in it's class you should set the parameters above -- and of cource include the file you specify at the correct path. After that your plane can be installed separately from others without touching the original buttons.