Okay, talking a very different approach. I realised that a big part of why I want pan controls is to use CV modulation to give me some nice movement (hook up 3x LFOs etc), so I switched to a voltage controlled panning circuit via dual VCAs.
Also added back in the Dry signal with its own pan controls, so in combo with @nervous_squirrel 's Wet Only mod everything can be nice a spatialise separately.
Any thoughts?