I was somewhat deceptive in my question gathering as I think this is entirely unrelated to the sixaxishelper, as I haven't actually gotten to use the wii controller until now.
I have tried removing and syncing the devices from bluetooth config menu and also bluetoothctlthey sync just fine.
/proc/bus/input/devices lots of things.
Logitech* AnywhereMX & K350 & K400
Sony Playstation(r)3* Controller & Motion Sensors
Nintendo Wii Remote* Accelerometer & IR & _Remote & Motion Plus (lists 4 inputs)
So my question could have been is the Wii Motion Plus incompatible? I searched the forums but I ignored that they go on and on without answers.
It syncs fine, and the jstest buttons respond, it is some mapping overlay, but also there is this Traceback in joy2key. It is very close to working. But very close could be miles, underground.
I would be surprised if this was successfully done by someone. The video for the screen is streamed over a proprietary 5 GHz radio. A gentleman in a previous post said it's based on 802.11n and he could very well be right. Still I think it may be possible through a custom USB adapter of some kind, though the 480mbps throughput limit may turn out to be a constraint, not sure. Is it possible? I believe so yes. Is it something easy to do, almost certainly not. You would probably need to find an engineer to design a custom USB adapter to communicate with the pad.
The USB port on the Wii U pro controller is just a charging port and doesn't do data. If you want to connect to the Pi via bluetooth you'll have to go into the bluetooth settings of the RetroPie. While you can get this to work, I highly suggest you get a PC wireless controller adapter. I tried hooking my Wii U controller to the Pi's bluetooth and it worked at first. But very soon I started experiencing ghosting to the point I couldn't even play the games. Using the adapter, I synced it very easily to my controller and Emulation Station recognized the controller very easily.
I know for my Wii U controller, I couldn't get RetroArch hotkey shortcuts to work as I wanted until I went into the config file and manually added the start button as the "exit" button. But it took me awhile at first to understand how the hotkeys worked (didn't know what hotkey option meant when I set up the controller in emulation station because it didn't do that in my Reys image).