FGear Vehicle Physics (v1.4)

Thanks for your answer, I have chosen the the second option. I really appreciate that the source code is fully visible, but I tend not to modify any plugin code, because if I decide to update the plugin later, then those modifications would be lost.

For anyone else interested, you have to call setReadInputs() of FGearStandardInput with false to disable the automatic updating, then you can call setInputs() with whatever pre-processed values you like.