If that's the case, could this also be used by the Obsidian board to tell an Emerald v2 board to switch color profiles?
Not with the current Obsidian. There's no pinout for a signal identifying which font is in use.
I'm personally hoping that the recent addition of Obsidian v4 to the parts store means that a new soundboard is on the way.
I know of another saber builder that builds all their sabers with RGB-capable soundboards, but offers the hilts in these configurations:
Base Price: Sound with single color
Upgrade lvl 1: Sound with Single Color and FoC
Upgrade lvl 2: Sound with FOC-capable RGB blade
All the same board, but different LEDs and wiring.
If US could combine Obsidian and Emerald into one new Diamond board offering RGB mixing and delayed crossguard ignition...