Hi source2!
It is a good idea i admire it. It can be done but u will have to design a big interfacing circuitary consisting mostly of buffers and gates which can drive next level comprising of your RAM and ROM .Make sure they are not loaded or overdriven.
Moreover impedance must be matched. If u are using diff logic families for ICS THEN FAN IN ,FAN OUT ALSO!
No doubt it can be done but why xcant u purchase one from the market?
;D