For gearing there is a merge request Draft: Choice of gear ratios for motorised microscopes (!352) · Merge requests · OpenFlexure / openflexure-microscope · GitLab. That just builds the different gears, and gains a factor of a little more than 2 on x-y. I also did some investigation of how to change the cut-outs to give more on z as well, and go further than 0.8:1 on x-y, on a local branch. I should put that on a merge request into the gears branch.
Ultimately working out a way to do direct drive with NEMA8 is the way to speed, but would probably need thermal management.