Lots of solutions, just picking the right one for your situation is the hard part. Everyone has an opinion on which solution is right, I'll list the ones I know of:

  1. Linear rails - mounted to the flats on the column and the dovetails milled away for clearance. A few have done this and claimed great success, but requires a large mill for modifying the column, and maybe even a break for the head as it reduces friction to the point it can fall under its own weight, also fairly costly in materials
  2. external mounted ballscrew and close up the column face (and optionally fill the column with granite epoxy or whatever). Probably the least difficult option on a new build if Z parts hasn't been made yet.
  3. build an "exoskeleton" for the column to stiffen it up, support the opening from closing in - never seen it done but in theory could help, would be relatively easy if access to plate material and plasma cutter or waterjet was reasonable (very rough, non engineered image attached). I'm kind of tempted to try somethin like this on mine from the point of view of improving what is existing, without blowing it all up for option 1, or rebuilding for option 2.
  4. Use a counter balance. This reduces the need to have the gibbs as tight, thereby reducing the amount of flex introduced due to clamping forces and the head weight pivoted off the dovetails. Also relatively non-invasive and can be added on to any build.