I have been collecting parts for a similar project.
I have so far got the slides (25 and 30mm) a 6.5" x 21" table
(part ordered from grizzly for one of their mills), and a
machine head on the way.
I was trying to decide between castings or laser cut plate
for the base and column. My neighbor has a cnc router, so I was considering
doing castings as well. My thoughts were to possibly make a manual and a CNC
version, but that is up in the air.