You are essentially demonstrating a MultiStyle on a DAW timeline. BIAB has had the capability to do everything in your list in this post for years.

With a MultiStyle if the user wants RT#3181 on bar 5 to also be on bar 21 simply requires clicking the appropriate Part Marker in bar 21 for RT#3181.
This can be replicated as many times as desired on the Chord Sheet and previewed.
Newer versions of BIAB has Partial Regeneration
Part Markers are Colored and can contain letters and numbers. Plus the Chord Sheet has Section Text
Users can adjust the volume for one section of a RealTrack or adjust the same for all occurrences of that RealTrack
BIAB generates the track according to the user input Chord Chart settings, style, tempo and Key

The attached screenshots are a PG Music pre-made MultiStyle demo using 16 substyles that can be placed on any bar. Every substyle can be repeated as many times as a user wants on the Chord Sheet.

MultiStyles are completely modifiable so it is quick and easy to replicate using all of the RealTracks used in your demonstration so the MultiStyle only affects the RealTracks and the Style would otherwise remain unchanged. The limitation of MultiStyles is user imagination and applying what's needed for a project.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
MultiStyle.jpg (329.47 KB, 71 downloads)
MultiStyle Changes can be on Any Bar.jpg (190.07 KB, 70 downloads)
BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.