As an additional thought regarding computers, it seems to me that participant B could be replaced by a weak computer in order to provide a consistent experimental setting. For instance, Leela Zero running just the current T2 network (no look-ahead) would provide an opponent that is probably at master-level strength and should easily be able to crush most human opponents who are playing unassisted, but would provide a perfectly reproducible and beatable opponent.
As an additional thought regarding computers, it seems to me that participant B could be replaced by a weak computer in order to provide a consistent experimental setting. For instance, Leela Zero running just the current T2 network (no look-ahead) would provide an opponent that is probably at master-level strength and should easily be able to crush most human opponents who are playing unassisted, but would provide a perfectly reproducible and beatable opponent.
[facepalms] Thanks! That idea did not occur to me and drastically simplifies all of the complicated logistics I was previously having trouble with.