Not sure if Gummo or anyone else has an easier way, but from my knowledge of this subject, most of the pad to different console projects are really frankenstein sort of things that someone does once just to see if they can do it. I don't think I've seen that sort of service offered.
Modding fightsticks is easy because all of the buttons are two contacts and you simply wire them to a board(s) within a nice big case--controllers most of the time don't work that way. They basically have the circuit right on the PCB and the button depressing onto the board completes the circuit. Because of that, doing an internal controller mod for a different console would be incredibly difficult.
This sort of thing is usually handled by an external to the controller solution, such as an adapter. Unfortunately, the only one that I'm aware of that is currently working for X1 and PS4 controllers is Cronus, which has a bad reputation. The "undamned" USB board would be a perfect solution, unfortunately, it currently doesn't support X1 and PS4 controller inputs.
