It's a good question that gets asked from time to time. However, it ain't happened yet! I think that there's a whole bunch of reasons. A prospective builder wants a machine that's just a bit bigger/smaller/faster than the reference (my own first router was to the JGRO design, but I tweaked dimensions to suit me), some want steel, some alu, some a mix. Building facilities/tools/skills vary, which changes the approach. And anyone motivated enough to undertake a project like this and carry it to completion probably has a few ideas of their own to include. After all, there isn't even agreement on which way X and Y axes run!

However, because so many of these ideas have been described in build logs, if you have the energy to plough through a good selection of them, there are plenty of ideas just waiting to be stolen. Sorry, borrowed...