Forget the slimline cd drive if you dont want too Cut your case . You can rute a cable out the pcmcia port or the scsi trapdor behind the amiga ... The worst is getting power for the thing i would use a power adapter meant for a usb - ide box.. Installing the ide splitter i strait forward and easy just follow the instructions ... But finding a good way to rute the cable externally is not always easy and require some thought ...
Try to get a kit like this
HERE use the power thing and just put the usb away somwere ,,, You can even custom make a exsternal cd case just cut a hole in it .. Try to get a long ide cable to this though---...