Emulator

What steps will reproduce the problem?
1.Map controls for an emulated Guitar or Drum extension
2.Load Rock Band 1 or (in my case) one of its Track Packs.
3.Try to use the mapped controls. Not working.

What is the expected output? What do you see instead?
Rock Band doesn't recognize the guitar and treats the WiiMote as being alone, therefore asking to connect a microphone to play.

Dolphin version with the problem? Other Dolphin version without the
problem?
rev6284

32-bit or 64-bit and any other build parameters?
64-bit

OS version and versions of tools/libraries used?
Windows 7 Home Premium 64-bit

Please provide any additional information below.
My guess is that the plugin was developed based on the Guitar Hero 3 guitar (considering it was the first one available on Wii). This guitar (as well as the GH World Tour guitar) is not compatible with the first Rock Band or its Track Packs (which are all based on the RB1 engine).
The drum extension has a similar issue, since it's based on the Guitar Hero World Tour drums. This one's not compatible either (obviously, because it didn't exist yet).
Compatibility with these instruments was added in Rock Band 2.
http://www.joystiq.com/Instrument-Compatibility-Matrix/

My suggestion is to make other versions of the extensions (or add an option inside) to differ Guitar Hero instruments from Rock Band ones, also considering they both have different functionalities and buttons.