Floyd Rose with a smaller neck...

It is my understanding that the string spacing on FR bridges is wider than a regular bridge, hence the Trembuckers that Seymour Duncan makes with wider pole pieces. Now since I'm more comfortable with a narrower neck, I've been thinking about putting a guitar together from Warmoth parts and i'd prefer a neck thats 1 5/8" at the nut. Most manufacturers are all 1 11/16" at the nut. Would the wide string spacing on the FR be an issue for a narrow neck?

I've played many FR guitars with both wide and narrow necks , and I have never thought of such a problem... Usualy the neck starts wider at the body , then goes narrower up to the nut , and both e-strings flow about the edge of the neck.
I think the problem might be the FR locking nut , but I believe there should be different sizes for different nut widths ... You should ask where you're gonna buy the neck if a similar one has been used successfully with a FR bridge before.

I made a quick search and I found a [41.3mm (1-5/8")] FR nut by fender.
Here.