I suggest adding following controls for jet-pack:
Shift - freeze in space (like on ladders in vanilla), until shift is depressed (or - until other movement key pressed)
Double-Forward - horizontal increase of speed, at a cost of fuel (like dash in vanilla), until Forward button is depressed
Less essential, but desired, for hover-mode only:
Double-space - fly up like in non-hover mode, until space is depressed
Double-shift - free fall until shift is depressed