I haven't read all the posts as it's so long.
But I did download your BIAB ARRANGER.MGX and had a quick look, the Arranger midi tracks was a bit late and needed moving forward.

If you want to bring a lot of midi tracks into BB use energyXT Vst

https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=518287#Post518287