A mate and I are finishing off a gantry machine using similar items and for exactly the same reasons. Scaled down from what you have in mind but very keen to see what you come up with. Used a KR33 on Y and a KR26 on Z and a ballscrew and rails on X. It started off as a portable machine but has turned into a moveable category.
I have some KR46's on the shelf that I would like to make a mill from so keep the posts and some photos coming.