a large part of the mods are done between apks and jar files with editing the smali in classes.dex (if done correctly anyways) so taking one rom and another and trying to mash will almost never work like notsointeresting said above. As for there not being much to choose from, theres actually quite alot for the shift, especially in the last couple months.
unofficial CM-9 builds
and many more.
theres quite a few devs busting ass and pumping out some quality work. your idea is nice and also like notso said, you def need to ask permission from other devs before trying to tear apart or manipulate a rom theyve worked hard on. there are some guides floating around though that are great assistance in making your own roms. sparksco, dodgejcr, one_love_420, and a few others i cant remember offhand have put up guides to help build kernels and compile roms. do a little reading and practicing and in no time youll be building your own custom rom too.
this by all means isnt an attack, just a confirmation of whats been posted already and some of my own opinions. good luck learning and building.