Guys, you forget you can easily Y-cable ANY board that has PWM input like that. Just Y off the cable for the ESC and run that direct to the ESC and board. You will lose a few things like inertia and momentum (if that board supports it) however you can always add expo to mimic inertia a bit. This saves on the board design and considering not many use external ESCs (just us regular guys) it isn't much for us to add one. On the manufacturer's side I can see why this was omitted as it isn't that hard to recreate on the user's side and cuts down on support for that feature. Any time a customer introduces an unknown variable to the mix it gets difficult for support to diagnose and fix.
I think its not bad actually, hopefully I get to try one!