the only problem with putting a locking nut on is that after you tune the strings, locking them bends the string slightly and they go out of tune. this is what the fine tuners on the bridge are for so unfortunately you need both ends set up.

you can put a floyd on a strat, its just a hell of a lot of messing around and if it goes wrong your stuffed (i planned to do the same to mine but i just bought an equiped guitar to save hassle).

i know how hard it is to keep a strat in tune when you use the bar. i used to do it all the time and frequently fell out with the guitar, hence getting a floyd rose. if you're gonna use the trem for anything more than slight hank marvin style vibrato then get a floyd rose, but i really would recommend against routing into your guitar. if it goes wrong you're gonna be seriously upset and for the money you'd actually pay for a good floyd rose (ie. one that does exactly what it says on the tin cos believe it or not some of them are completely useless) you'd be just as well getting another guitar.

what about some kind of super strat type?