So, I tried mapping controls for planes to a HOTAS setup, and noticed some very glaring issues with control customization.
These problems most importantly, not being able to toggle relative control on an axis, not being able to bind each axis individually for multi-axis controls (it tries to do it, but it always ends up with binding the x-axis as the y-axis and vice-versa) and not being able to set buttons to toggle instead of hold.
There are also other issues relating to controls, but I believe those issues are bugs, and not relevant here.
All of these mentioned missing features would be pretty easy to add, and hopefully mentioning these features now might allow these absolutely required features to be added soon in the future.