Very hard to gauge from the photos but, flying blind, I'd be interested if you can keep the rails for the X-axis as-is on the bed, strip the gantry out and look for the top half of the cabinet as a full machining enclosure. Build your own gantry and Z-axis. The 25 micron accuracy of the screws is not too bad - look to re-use but use a belt-reduction for positional accuracy. Much depends on how solid the base is, though, as the machine was clearly designed for a different purpose.

My own bench built for an original plan for a 800x400 router weighs in at about 250kg, so depending on your actual goal for your machine the base /may/ well be suitable - and takes a lot of work away from the build. But you need to approach this with eyes wide open.

Tallinn, eh?, was there last month, think I spent more than on my mill frequenting the Põrgu bar :)