I'm so happy you're doing this, faderfox! I was trying to piece this together today between the available controllers on the market, and here you are doing it for us.
My favourite out of the 3 as they stand now is PC12, although I would like to see another row of buttons.
I agree 100% with Rocketnumber10, re encoders vs pots. For a device-specific controller, being able to see the state of each parameter is crucial. As for EC12, if the encoders all had LED rings, that may be doable - but the increase in cost would make me just want PC12. I'm not sure I see the value of the encoders over pots, other than feel?
It would be really nice if the rows of pots had configurable colours that could be changed between different pages/configs.
For me, the ideal controller would be a cross between PC12 and MX12. One row of large rotaries on the bottom for track level (like a rotary DJ mixer), instead of faders. 5 rows of pots above that (or 4, but 5 would be ideal). 2 rows of buttons on top. I would be using this without a computer most of the time - but if there was the chance to have a small grid of buttons on the side for Ableton navigation and clip launch, then this would be the controller of my dreams.
I would buy this today.