hi
yes very doable... if you just want digital in/outs, you could have lots using a binary decoder like the CD74HCT4514. that will take 4 pins and turn them into 16. The one problem with getting enough outputs is finding a chip that has, say, 64 output pins. You could also use a shift register, like the Philips 4794 shown in this tutorial, but you sould have to check and see if the outputs can be set to "open collector" state when you are shifting the data in, so that your relays would not get triggered in domino-sequence fashion.
D