I Actually have good news, The mayflash GCN to WiiU converter does in fact work on the PS3 if you set it to it's PC mode
I was lurking around when I noticed this thread and remembered I had the mayflash converter, so I thought I would try it out for you
The Analog stick on the GCN controller doesn't work on the XMB menu, but works in game, I only tried in KoFXIII because I had the digital download of that title and was too lazy to put in the BB:CPE disk.
But I can check for you really quick
The buttons are
A=cross
B=Circle
X=Square
Y=Triangle
R=R1
L=L1
Z=R2
Edit: on further testing, the analog stick diagonals don't work, so this might actually be a bust, I'm sorry for hyping you nothing
Double Edit: the diagonals worked in Blazblue for some reason, I don't even know anymore, I hope this helps someone