So i messed around with this when i saw your post a few days ago. I was able to get a version to compile that allowed the wii u pro controller to connect, but inputs didn't work. Im not experienced with C++ at all though so i was was mostly just following the instructions on the libwupc github. The issue i ran into was calling WUPC_Data, as i wasn't exactly sure where it needed to be called. Im also not sure if once libwupc is implemented it just runs off of the input code that exists or if new code needs to be written.