Hi ste, I tried exactly the method you have above. It could be quite powerful, but is very difficult to get the hang of. At the moment I am playing with a setup like you have there, but with thrust and yaw completely removed, at least until I am more comfortable. Haven't really missed thrust and yaw since I unbound them, still I might turn them back on at some point.
I do like to have the pitch and roll on different sticks tho, must tie into some ancient muscle-memory from the BBC B when we used S, X, <, > keys.
I'm starting to think this might be the game that persuades me to get a HOTAS though.
That was my thoughts, I didnt have a yaw in the original. So maybe I could happily live without them now, except I think you might need it for landing on a space station.
The original I used good old QAOP on keyboard but I dunno whats for the best now, I'm still trying different setups.
I remember I bought a joystick especially for that X game, and I didnt like it and ended up using keyboard.
I would like to be able to use the DS4 as I think they are generally better than big sticks.
Its basically trial and error at this point.
Maybe like Michael said, the best bet is to map it to the dpad.
But the good thing about my set up it is possible to roll, pitch and yaw at the same time, could be good for evading fire and tight movering once the hang of it is... erm, achieved.
Vertical Thrust, plus pitch, plus roll, plus yaw can make your turning circle much sharper I imagine.