I fix this sort of stuff by multiple generations to .WAV file and edit what I want in a DAW.
But for those of us who prefer to stay and work within BIAB, it should be possible to regenerate parts of a track, just like RealBand can.
If one prefers to stay and work within BIAB, it is both possible to regenerate parts of a track, have more than a total of 8 tracks and even multiple audio tracks just like RealBand. Well, almost anyway. You can have 48 or more tracks and multiple instruments, multiple styles and dozens of effects in a Band in a Box project but choices have to be made early and commitments to sub mixes made before the final mixdown and a DAW is not required to do this.
The method utilizes the analog multi track recording techniques of overdubs, Punch in/out and Bouncing. Issues that modern recordists have with this method is the necessity to commit to sub mixes and Fx's and also not having discrete access to each individual instrument and track throughout the entire project.
In Bobby Owsinski's third edition of The Mixing Engineers Handbook, Mr. Owsinski includes interviews with 36 of the world's top mixers from nearly every music genre. Each and every one of these engineers make mention of the change in the projects they receive that the artists, producers and record companies that now have the ability to save unlimited tracks, they receive projects with 25-30 guitar tracks, vocals, BGV's, even solos that have to be auditioned, culled and comped during the final stages of a mix where these tasks occurred before a project was sent out to a mixer in days gone by.
It can be done but is certainly not a preferred method. Nothing wrong with the new way at all and home mixes today are much better sounding and professional sounding that what was available years ago.