Thank you for the compliments. http://www.vicious1.com/donate/ if you are so inclined.
I need to make a FAQ now as this comes up a lot.
Acrylic is easy to cut, other than maybe bracing the 1.5m outer tubes I doubt you need any modifications.
1″ is the wrong size, you would need to redesign the entire machine to fit. Every single piece.
Solid bar is only slightly stronger than tubular in a supported cantilever setup (http://www.engineersedge.com/beam_calc_menu.shtml), and negates its benefits with its added mass. Not to mention price.
23’s are over kill. If you are worried use larger 17’s. this uses 2 per axis one on each side overcoming most machines weakness of 1 sided pushing (try using a broom with one hand vs. 2).
You can use mach 3 if you prefer.
You don’t really need the BOB with this it is very easy to move by hand. Other machines are tedious to move hence the bob.
Acme z axis major benefit would be plunge speed, precision doesn’t seem to be an issue. downside, cost, redesign.
1.5kw spindle is overkill for acrylic, you could easily use a cheap dremel.
6mm gt2 belt has a working strength of 6.5lbs and a breaking strength of 125 lbs and there are 2 so double those numbers, why go larger? You would also need to ensure it fits or modify the drive train to accommodate a large belt.
Boils down to please try the machine as is before you modify anything I would wager that you will be more than satisfied.