I would love to see you do this. P90s and 3-way toggles are high on my fave list too.
The guitarist in Warrior Soul had a Strat with two P90s, his sound sliced my head off! Truly amazing.
Just to note though, the true P90 is the 'dog ear' pickup that was found on LP Juniors, the humbucker shaped one is a 'Soap bar'. Soap bars sound good (sometimes P100s) but most P90 fans insist on the Dog ear type.
Dog Ear
Soap Bar
The Dog ear is surface mounted (Gibson did this to keep costs low on the no frills Junior) with just a small route for the pole pieces. Where as the soapbar fits like a humbucker.
I think you would be able to fit soapbars, may need to cut a new guard though, but dog ears sit high on the body which would mean raising the bridge high and shimming the neck.
Anyway, hope that helps.
If your looking for any other ideas you could consider Rickenbacker 'Toaster' pickups or Gretsch Filtertrons. 😉
