If you are wanting to do a belt drive like that I believe that @MeticulousMaynard has done something similar with his Z Axis. He also uses that kit that you linked I believe and then builds a frame around it.
I went with my own concoction of an openbuilds C Beam with V groove bearings and then I got a gantry plate from amazon mainly because I thought I could do it cheaper than the pre built one on openbuilds. However, I realized that I still needed their lead screw and then I also had to make a shim to mount it to the gantry plate that I had purchased. Finally, by not getting the open builds one I realized that theirs is inset slightly so that you don’t have the problem that I do where screws get in the way of the bracket and I had to make a dimple in my 3d print so that it would fit.
That being said, if I were to do it again I would probably just pony up the first time and get their bundle and then modify it to my given router.
Hope this helps.