Just to chime in quickly here about the packet side:
I guess a smaller vision would be to see a software
TNC like direwolf
that can natively support more than one over the air baud rate.
This is already possible today with Direwolf using .asoundrc tricks.
The problem is, all other stations on frequency won't necessarily
recognize this faster mode as a valid signal and thus possibly double on
that signal. As such, it's better to use other frequencies for newer
modes. All that said, I do understand your desire to support a
"transition" approach.
--David
KI6ZHD