Thanks guys, this has been helpful.

Humbuckers definitely don't fit in this P90 route, as Simon says. I'd tried already, but no dice.

I have a plan for the guitar that would see it changing hands (provided I am satisfied with the finish), so I guess I was just worried I'd be limiting that persons options. The more I think about it the more sure I am that a humbucker will give me the look I want, so will have a crack at re-routing once I'm back from Mildura.