Guys I have two towers here that are modded in exactly the way you intend to do yours!
the floppy drive is not a problem! get a pc twin drive floppy cable and chop the end with the twisted bit off! the length will go from the a1200 board to drive DF0:
both towers have external drives mounted inside the tower cases! again use a long length of floppy cable to join the drive to the controller board! i had to mount one drive in a 5 1/4 adaptor bay as my blue case has only one 3 1/2 bay and its covered with a funky cut out and button!
*i even have the external drive ports at the back to allow another floppy drive to be chained on! i managed to get them onto 25pin lpt blanking plates that you used to get with old AT motherboards!
And now for the proof! im going to take a shit load of piccys and fish out all the other stuff i did.. planning etc and whack it on some webspace so you can leach my ideas