I know 250k is the preferred value for singlecoils, but is there any reason you can't use 500k? What are the likely effects, slightly more open high end?
If it's a really bad idea, is it possible to wire a guitar with extra resistors in line between the pickup and the pots to replicate the effect of 250k pots?
Theyll just be brighter. Honestly, i think for you, it will be perfect