Just a heads-up - the PS2 controller compatibility chart is slightly incorrect. The GH Kramer works with everything that the SG controller works with, including RB 1 and 2. Also, you might want to separate GH3 and GH:Aerosmith, as the latter game added support for the RB Strats (as have all games since GH:A). Interestingly, all PS2 GH games since, and including, GH:Aerosmith actually support the use of applicable 360 and PS3 instruments on the PS2 (which, at least in the sense of RB kit, are identical between PS2 and PS3, and obviously means that no drum kit works on GH:A). The PS2 RB games only support the original-style GH controllers that attach to the PS2 controller ports along with the PS2/3 RB kit. I have personally used a 360 RB1 drum kit successfully with GH5. Not sure how it works as I've never tested it, but the files for both GH:WT and GH5 (and likely GH:Metallica, GH:Smash Hits, and GH:Van Halen as well) have support for "PS2 USB Adapter", and GH5 also lists support for "360 USB Gamepad", but I'm not sure how much use the latter would be (except for a vocalist).
List of strings found in the file BCUI.IRX on the GH5 disc:
PS3 GH3 Guitar
PS3 Rockband Guitar
PS3 Rockband Drums
360 Rockband Guitar
360 Rockband Drums
360 USB Gamepad (!)
360 GH2 Guitar
PS2 USB Adapter (!)
PS3 GH4 Drums