There's ways and means. Elbox still stock the tidiest and cheapest (new) IDE splitter that allows use of 2.5" IDE connectors mixed with regular ones. Check around for 2nd hand splitters, sometimes they pop up (though not often).
Or there is the Squirrel SCSI interface, they pop up 2nd hand sometimes too ...
The power would need to come from a PC power supply (or you can get external 5.25" drive enclosures that also have a PSU in 'em).
Yes you would need a CD filesystem, there's a couple of freely available ones that work nicely. An IDEFix needs it's own driver too, but the natty little Elbox splitter does not!
A harddisk won't be affected by another IDE device being added, as long as they don't clash in the IDE setup (ie. a max of one master and one slave per channel).
I think that covers everything ...
