Elven workers

I would like to change elven workers that when they are captured they still can build improvement on forest. How to do that?

Atm the ability to build anything on a forest is a per civilization thing so the easiest method would be to edit the dll I'd guess or possibly there is a "on improvement built" thing in the python code somewhere that you could edit so that it would put the forest back on the tile once an improvement was built by an elven slave. The python editing would have to be very precise so that you don't end up with forests on desert tiles or flood plains or whatnot.