I believe the answer is No.

Really interesting question. You have given a thorough description, and you tried the solutions I remember trying many years ago. I applaud your method.

Unfreezing is necessary to transpose, as you discovered, and of course that will change the track since that's a feature of BIAB.

Since you have BIAB 2023, you now have the ability to regenerate a part of a track, and with patience, perhaps you could reconstruct a track you could live with.

It is true that once you convert it to an audio track, you will experience the mixer track color change and there is no way I know of to go backwards. For that reason, I sometimes do my transposition using another program, and that leaves my BIAB track alone in case I ever did need to revisit the song. The catch, and yes, it's another big one, is that no stereo editor can transpose much more than a full step, at best three half-steps, without introducing artifacts.

No one yet knows, but since it is a stated goal of PG Music to make the tracks more 'equal', perhaps in a future version of BIAB this problem will be addressed. By this I mean, you can transpose MIDI all day long, or change the tempo, with no problem. I don't know if it's technically possible, but a Wishlist post could ask for some way to keep the content frozen when otherwise unfreezing the track for transposition. I suggest this because frozen tracks are not saved with the song as full audio tracks; only the instructions are saved to play back the frozen track as those instructions dictate.

Hope that made sense.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.