I guess there are too many tastes out there, and it will have to be configurable more extensively. Probably going to throw a bunch of checkboxes there.
For example, why pitching with mouse is ok but tilting (as if you were sat on a flying platform that tilts on turn) is not? I originally blocked both because both are something that is outside of your own willful head movement, and pitching induces nausea as well. In a short while I got used to it, then to the tilting as well.
I guess the problem is in the middle grounds - people who can't stand any externally induced motion simply won't touch the mouse, but the intermediate step to being able to handle a tilting horizon is pitch + optional levelled turn?
If it should not tilt, should it turn while keeping the level? Or completely ignored?
I'm still not sure, so let's fill a table, flight mode or UFO mode in VR (and optionally normal mode, not sure if there's any difference between stereo/mono mode):
vertical mouse → [pitch/climb/-]
horizontal mouse → [turn/tilt/strafe/-]
automatic movement [ ]