#1
are they neck pickups realy different from the bridges? dont you just have to turn the pikcup around to lessten the output?
#2
usually on strat the bridge pickup will have slightly more output than the other two. i beleive they have more windings in them, but im not sure.
#3
Bridge and neck pickups don't have to be different, but typically the bridge has more output. And no, flipping a bridge pickup around doesn't make a neck pickup. The output would be the same, but different frequencies would be emphasized.

It all depends on what you're trying to do. If you want to take a guitar and make it a high output metal machine, you can take the bridge pickup, move it to the neck, then add a high output pickup in the bridge. Save some money that way. Of course that's if the two match up well together. Picking pickups can be a fine science if you're trying to get particular tones.
It's a fine line between clever and stupid.