It's worth building for sure and it will do a perfect job as a great sharpening system for you. The one I have left available for free on tinkercad, is my old version (the same version
CelloDan
posted about here. It works well on a MK3S, printed in PLA with 4 top & bottom layers, 3 perimeters and 25% rectilinear infill.
Seeing that you already have a great printer and know what you're doing with 3D printing, I would definitely say make one for yourself! Post about it here when you're done or have questions.
FYI, Gritomatic will soon be selling my (much improved) new version, with a lot of upgrades and refinements. The new version won't be available for free. That said, the old version will work perfectly fine and does a great job.
As far as stones are concerned, the AliExpress cheap diamond plated 1x6 inch stones are perfect. Just make sure to lubricate them with weak soapy water when sharpening (a few drops of dish soap mixed with water in a squirt water bottle does the job).