Paul, the reason for forcing 2:1 is that that is the official format aspect ratio.
Personally I don't mind either way, as it can be changed to a degree afterwards. Also, equirectangular isn't really the best format for storage of 360°. As you would be aware the poles become distorted, and have excessive resolution, with heavy antialiasing.
Ardour is a GPL DAW that has ability to split buffers. Hence why all LV2 plugins always need to know the buffer size (not the sample rate, that's set).
This allows as you said, a buffer to work with timming that are between buffers.
I don't know how this would work in a live context, as Vuo would need to know in advanced where when to split the buffer. Which would mean that all incoming data (MIDI/OSC/controll) would need to be delayed by one buffer cycle.
I think that would be ok, given the benefit it would bring.