IIRC the cup has manual mirrors, so no wiring to the mirror, which suggests a different door loom. If the car loom as the same, then you could take a power mirror, replace the gubbins with manual stuff but retain the temp sensor, and replace the door loom, then you just need to work out how to update the display.
Having looked at adding power fold mirrors to my FF, it looks more complicated than that, with suggestions that the FF with power fold mirrors has a different loom to the FF without. This suggests that the Cup will certainly have a very different loom, essentially making it unfeasable.
Hard to get an answer without in depth interrogation of the parts software to identify just which parts (looms, modules) are different.