No, your project sounds very useful, especially for odd time signatures. I am only commenting on what I observed to be the root cause for the confusion on 12/8 time in BIAB vs. your DAW - which is the issue of dotted quarter vs. quarter. In Pro Tools there is a setting for this, and in MuseScore there appears to be as well. In some other DAWs it looks like there isn't a setting. They think of 12/8 as a simple time signature with 6 normal quarter notes, which is very strange, but is normally of no consequence because they aren't notation programs. You should put in a feature request for Reaper. In the meantime it might be simpler to set it to 4/4 and use the same tempo, rather than trying to do tempo gymnastics.

Andrew
PG Music Inc.