Just from a pure tech perspective:
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Cantabile doesn’t have access to buffer settings for all ASIO drivers, e.g. for RME interfaces, Cantabile is just “informed” of the buffer size, but can’t change the buffer size. For that, you need the specific RME app. So this feature would be an automatic no-go with RME interfaces
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Changing buffer size will probably not be possible without turning off audio processing, turning it on again - essentially a full “engine restart” with a config change in between. Since this can take a bit of time (on my system, a pure engine cycle is a 2 second process - add to that the time for a buffer size change in the driver), possibly not something I’d want to change in a live setting between songs, TBH
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also not sure how such an engine reboot might interfere with the process of setting up the song when trying to do things in parallel, so it would probably be: turn off the audio engine → load the song → turn on the audio engine with new settings. Overall quite a bit of down-time between songs.
I’m not much of a fan of open-heart surgery during gigs - I try to optimize my setup so that everything runs nicely at 128 samples buffer, so I don’t run into this requirement 
. Any song that scratches the limit gets brutally simplified, and any plugin that hogs resources gets replaced.
And TBH, I wouldn’t let Keyscape near my live setup - this beast opens so many resources and file handles, it’s not even funny… Yes, it may be the “ultimate” realism for some instruments, but given the battle for acoustic space in a typical rock mix, nobody is going to hear the difference between Keyscabe and VTines / VReeds in a live setting…