If I understand the OP correctly he would like to transpose without regenerating. So, if a particular RealTrack has distinctive riff components on bars 1-4, then after transposition that distinctive riff would still be on bars 1-4 but now it would be transposed.
I think this presumes that each distinctive riff component is present in all keys or that BIAB can transpose those riff components successfully.
But I wonder if that is the case. On many occasions I have noticed solo RealTracks seem to offer different riff components in different keys. I have had RealTracks producing an awesome riff but when I change key and regenerate (many times and even with Multiriff) I cannot seem to find the same distinctive riff.
Does anyone know if ALL unique riff components are available in ALL keys on ALL RealTracks?