Yeah, if the GCP only transmits CC messages when it's in Instant Access mode, that wouldn't work… even if the Factors could switch algorithms via CC, it would require a separate message for each parameter within each preset. Much more complicated than a single program change message.

Wouldn't the 4 switches along the bottom still be available for program change transmission, even in Instant Access mode? (GCP UM p17) That could allow 4 effects to be accessed (or 3 effects and a bypass) without having to switch GCP banks.