Emulator

Hi. This is Koetsu/StackOverflow0x.
There's the attached screenshot of it working, as you've probably already seen. Hopefully it can be properly implemented in Dolphin now with some button support.

For reference, here are the Gecko cheats I made which are working for me on the NTSC version of the game.
$Fake Pro Keys (Player 1)
289E9B82 00000C00
0490B5FC 8086B771
E0000000 00000000
*Press B+A on P1 Wiimote to activate
$Fake Pro Guitar (Player 1)
289E9B82 00000410
0490B5FC 8086B74D
E0000000 00000000
*Press B+Plus on P1 Wiimote to activate
$Fake Pro Keys (Player 2)
289E9B82 00000C00
0490B698 8086B771
E0000000 00000000
*Press B+A on P1 Wiimote to activate
$Fake Pro Guitar (Player 2)
289E9B82 00000410
0490B698 8086B74D
E0000000 00000000
*Press B+Plus on P1 Wiimote to activate
$Fake Pro Keys (Player 3)
289E9B82 00000C00
0490B734 8086B771
E0000000 00000000
*Press B+A on P1 Wiimote to activate
$Fake Pro Guitar (Player 3)
289E9B82 00000410
0490B734 8086B74D
E0000000 00000000
*Press B+Plus on P1 Wiimote to activate

This will override whatever was being read by the game due to the Wiimote controller extension setting in Dolphin. By just poking around at memory values, this address (00a8a440) will change what the connected "extension" is read as. It should be a 01 which means Guitar = Guitar, but changing it to 03 or 04 will make that extension always read as the keyboard or the pro guitar. And when it's simulated this way, the mapped controls let you play the track, to some extent.

That's the best I can offer on this right now.

These enhancements don't relate to wiimote extensions; the Rock Band instruments are all USB devices i.e. it would be impossible to enhance the current Drum expansion to support PRO cymbals since they aren't compatible hardware.

At least for Drums, it's already listed as an extension in Dolphin's Wiimote menu even though the game uses a USB to connect it. The game wouldn't let the cymbals be selectable if they weren't being detected, so that's some progress.

The Pro Keyboard is bluetooth through its dongle and I think the same goes for the Pro Guitar but I don't know for sure.

The Rock Band drums are not available as Wiimote extensions. What you're seeing are Guitar Hero drums, which don't support the full set of 3 cymbals.

What would it take to get it to work though? I figure it's just sending slightly different inputs.

As it is now, when Drums are connected, they are read as "wii_rodrums" by the game, which are probably the GH ones. When the RB2 Drums are connected, it should be read as "wii_drums_rb2". But it might not even matter.

Right now, it is possible to hit the different notes, but just using different buttons. Like, the 1 button is read as a yellow pad hit while the actual assigned yellow button is the hit for the cymbal. If I set up some test notes, it should be possible to see which ones can already be hit.

Apparently, since it is emulating Guitar Hero drums, yellow is read a yellow cymbal hit, and orange is read a green cymbal hit (the rest are read as a tom hit).

on the wiimote, the drum notes are mapped like this, in the order of a typical RB drumpad: B 2 1 A (all are tom hits)

So technically, the blue cymbal is the only thing it's missing. So you can practically play using an actual Pro Drums setup if you wanted to, just that you won't be able to make use of the blue cymbal. :P

if this has already been discovered, I apologize. just giving a heads up~

I wish Keyboard was emulated. I wish I knew how to program and add the extensions. Maybe I should look into it.