Oh man, not this again.
1. If you only have the double-bass version of a track, you alienate users based on playability. Whereas on the other hand if you only have the single-bass version of the track, you alienate users based on preference.
2. The choice between a single-bass and a double-bass song is fine, as long as it doesn't prevent a different song from being released.
3. Under the PS3 users current situation you cannot have the option for both a single-bass and double-bass track without preventing another song from being released.
So unless you're okay with either alienating users based on their ability to literally play the track, or you're okay with having even less songs ported from xbox360 RBN you cannot agree to have this.