GoPro isn't stabilised unfortunately. M4
/3 is a pretty good choice (I like the OM
-D) and a huge range of lenses can be used on it from various makers via adaptors if you can't find a suitable native m4/3 lens. The OM
-D stabilisation is excellent, and it's smaller than DSLRs - esp the lenses - which may be a factor in finding somewhere to mount it.
But you are also dealing with some basic photographic problems which go beyond the camera type. You want inside and outside the cockpit to reproduce well. The problem is the range of lighting involved will generally exceed the dynamic range of the sensor - you can correctly expose for outside with black inside or expose for inside with white outside. You may find a sweet spot in certain conditions which allows you to get some detail both in and out the cockpit, but it won't be pretty!
Usually it is necessary to use an exposure which works for the outside and then artifically illuminate the interior (flash).
An alternative would be to use two cameras, suitably mounted, one set for exterior and the other interior, then combine the image/video in post processing - but that entails a whole other set of skills which you may not want to get into.
Colin K. Work, Pixstel