SeriesII Quill Zaxis CNC addon ideas: Like Jon E's?

I was wondering if, in the future, it would be feasible to add
a ballscrew mechanism to move the quill of my older seriesII model;
where the knee is the Z axis. The quill at one time had
the air-driven-spindle-wizard-rotary-depth-stop-thingy( technical
term ) which I removed.
The mill has a larger 4.25 diameter quill that is a little 'sticky'
to move. A previous owner put way lube thru the quill I think at
some point. It has has gotten easier over time as it works out.

I remember seeing a picture of Jon's setup where a 'clamp' is
attached at the end of the quill with a ballscrew to move it. I also
saw on Ebay a mill just like mine, but they had some weird ballscrew
setup on top of the head that appeared to work straight down the
drawbar entry hole. My quill doesn't have the drawbar hole that goes
all the way through to the tool holder. Its a quickchange type 40
taper. Options I'm guessing at are:
1) Using the depth bar that moves in parallel to the quill ( sturdy
enough? Offset force issues? ).
2) A clamp on the quill and several ballscrews to drive it up/down.
3) Something through the center of the quill. Probably disassembly
and modification needed to the quill.
4) Just use the Knee and shut up :-) most likely what will occur.

Thanks for any ideas.
-Lee