Question for you:
I know IDE stuff is easier to get nowadays, but I am concerned about the practicality.
As far as I can figure out, I'd need an IDE buffer thingie (as I have a hard drive already). Then trail the cable to the CD ROM out the back somehow, to an external drive, which seems like a bit of a mess.
The reason I considered SCSI was mainly since with something like the squirrel, it seems a bit neater and easier.
Any easy / practical ways to set it up, without making my poor miggy look like she's on life support? 
Im currently leaning towards getting CD ROM last, but it never hurts to think about it ahead of time.
No. All that stuff about needing a buffered IDE interface is just propaganda that Eyetech deployed so they could flog their 'Buffered interfaces'.
There are some photos on here of Amigas with custom connectors on the side to attach IDE devices, all you need is an adaptor to convert the 44 pin header to a 40 pin header. You will need a seperate power supply for the drive. You also have a PCMCIA slot free for a wireless card.
At this point, putting the Amiga in a tower case becomes tempting.
Think Franko had a similar type setup, but I could be wrong about that one.
All the best.