P-Rails on a Heritage H170

[samiamy2k]

I'm totally stoked about the new P-rails. My thought was to put one in the neck and keep my JB in the bridge for a really wide range of tones. Problem is that I keep reading that they should be matched in pairs. What would be the downside of just installing a neck pickup, and how does one get single coil, P-90 and humbucker without installing an extra switch? I already have push/pull pots on both pickups, but it seems I'd need one more position to access all three options on a P-rail. All thoughts would be welcome.

[Phostenix]

Does your guitar have pickup rings?