XP is hardly any different to VX - the principles are the same. The differences come mostly in the locations of certain methods and the way in which certain processes (like the battle system) handles.
I've already translated one script I did for VX to XP for someone, and I've also nearly finished an extension onto an already existing script for the same person. I was a little unsure how it'd go to begin with, but really, there's little to fear about writing scripts in XP, especially if you do VX. Just handle the change in the same way you started writing for VX and you'll have no issues really.
As for this script request, I'm gonna make a start on it now. Hopefully, my already worked out attack plan should work meaning a quick finish - of course, we'll see when it's done and it tells me all the errors I need to fix and all the bugs I need to kill.