Here is how I got my zoom/FOV to work smoothly using xpadder.
I tested using mouse button 5 + mouse Y axis and the cockpit is clickable at any FOV/zoom level so the devs
could just add a new binding to the game for smooth zoom.
Also I managed to bind "mouse button 5 + mouse Y axis" to the left POV on my Saitek x52 using Xpadder (the Saitek software wont let me bind a mouse button
and mouse movement to one button

) so smooth FOV change is working pretty well for me now.
I wish I didn't have to run xpadder to make it work, but at least I got my smooth zoom back (and it works with TiR).