Hi pitchslap
I replied in the other thread with some info but some other things that might help with tracks is to manually crest a Pip and copy and paste into it for now.
I've not used the move tracks into subproject much due to what you mention but I'll try it again today.
As for naming, you can change how the name appears in the master I think in item properties without an issue but you might be stuck with the actual file name. I think if you folder the tracks first then reaper uses the folder name. Not ideal but something for a needed option menu!
For me, I'd like what I've mentioned in the first post which is for a bit more "logic" in that action that will better include the time selection and maybe even only move the stuff within the time selection to a new subproject but leave the tracks and items behind still if there are items outside of the time selection.
This way, you say" section off" your verse drums and then your chorus drums so you can treat them with different mixes etc.
Another big addition would be that subprojects should be able to route their master output back into the master project and "come out" of the actual item in the master project so the mix doesn't change and is in context.
As for sends, remember you can have the subproject route out upto 32 (or 64 maybe) channels to a single wav so you can do some clever routing stuff still inside the subproject.
As for bit depth. I've not tried it yet but go to render settings inside of the subproject and see if the bit depth option there allows for 64 bit as the online/offline option works there too so maybe..
I personally wouldn't bother going past 32-bit and even then for me, the benefits are more about not being able to clip the output as you can go past unity/0dB in a float file. Some people have asked for an option to have subprojects render at 24bit instead to save disk space and I might even change it there too if we had the option.
Anyway, I'll mess about with move tracks to subproject later and see if there's a way around your issue.