There are many posts on this forum that address an action that is currently difficult or impossible to do in BIAB. I have found it very useful to use an external MIDI/audio sequencer to 'take over' many of these tasks and help produce the final product that you had in mind as a stand-alone product. Such things as changing styles in RT within a song can be done in a straightforward manner by creating separate versions of the song with the desired changes, rendering each in BIAB, and editing and mixing the necessary tracks in the sequencer. Further, MIDI editing (and converting to audio) is pretty easy to accomplish in the sequencer, as are a number of other useful actions. For years I have used Metro SE, which is reasonably capable and is inexpensive compared to the BIAB investment. I understand that if you need to remain within BIAB this approach will not help at present, but if your goal is a single complete audio file it is certainly the way to go.