Resisters are cheap. You can buy a bag of a couple hundred of various values for just a couple bucks. Lets you do a lot of experimenting for just pennies a shot. I like the idea of using 500k pots and, if necessary, resistors for the singles. But the CC definitely needs a 500k.
I don't know a lot about singles, but I'd expect that the STK-S4s in neck and middle would suit you.