i think the point of that mode is you alter the tone by adjusting the blend of the amps rather than going nuts with each one. IMO it would quickly get bloated and overly drawn out if you had total freedom to adjust everything. It’s also just replicating exactly how Mayer dials his amps and sets things up in the studio - it’s his plugin after all. Nothing stopping you doing your own complex routing with multiple instances if that’s important to you - it just wouldn’t be a John Mayer setup anymore, it would be your own rig.
It’s a novelty/party trick feature, but given it’s done with John’s own gear in his own studio, it’s pretty cool to have on hand.