If it helps you..you can use the USB host mode on Android 3.1 to connect all manner of USB devices including an external HDD. If its a mini and not self powered you still need the power adapter and AC. At least mine does...it won't spin by itself when connected. It will read and write NTFS though.
You'll need to root the device and install a custom version of the kernel though. Its not that hard...but it will take you an afternoon. Well worth it though as you can Overclock to 1.4 and run sick video playback (rumors say its been OCd as high as 1,7)
I don't know if you can attach an external DVD. Not sure it will take that video input but if you think you may want to go Droid...google and see if anyone else got it working. A better solution is to just rip the files (DVD Catalyst is awesome for $10 and will do this with pretty good cpu management) and load them on a samba share which you can transfer to and from easily to. That's what I do anyway. If you have a static IP or dynamic dns you can set up FTP access to your Samba shared drive to get the files on the roadm. That's also what I do.
So far I havent seen any of this done with iPad (I have Android tablet - the Xoom, hubby has iPad2.) Not trying to jump on iPad's functionality here...just trying to help OP get the device he needs to run his tech. Don't want to see the guy/gal waste hundreds of dollars.
Sent from my Android 3.1 Motorola Xoom Tablet!