I think there should be a 6 cylinder version of the RB4. Maybe with a 3.0 inline 6? Maybe even a V6.

I would rather see RB2 - front wheel driven non-aspirated version of RB4,which should be performance matched to XFG and XRG. Could also be added to demo lineup.
Also RBR (RB4 GTR) idea has been traveling around the forum,but not sure if we need another 4WD GTR car. Personally I would rather see some RB4 and Group B rally car fusion as a rallycross car,but then again - there aren't much areas to race such car yet.

The 6cyl version would be fancy along FZ50