Road FD with a Half step triple should be OK, the cage back plate is shallow
and so reasonable when the 2 chainrings are about 4~6t difference ..

3rd chainring might need to be like a 30t, so as to not drag the chain on the bottom spacer.

not much benefit with a 9+ speed cassette.

Mavic made VTT derailleurs too, their MTB designation, French.

You may find a 130 bcd triplizer from TA, new, At Peter White..

I think the 3rd ring is a 74bcd..