I looked at a lot of self built and production routers when I designed mine and took from them what I thought was a good feature and that could be done in my shop with the tooling I have. Mine ended up with a 49X97 4 zone vacuum table and a 51X100 cutable area to allow for triming a full sheet to size. I spent a good bit of time fixturing mine to ensure it would end up square when done and to control any weld distortion as I went on the frame work. A good solid base is what will make the machine a good one in the end. One of the things I decided to do on mine was use good quality linier motion rails for all axis and this did add to the cost but after fine tuning this thing I think it is worth it for the accuracy they provide. I use mine to engrave lexan for Harley windshields at .004 deep and it will hold that and repeat. It is rewarding when you get finished to watch a machine you built run. Some good sources for parts are http://www.kelinginc.net/ for motors and drive components. http://www.k2cnc.com for a Z axis (hard to build for what they sell them for) http://www.machsupport.com/ Mach 3 to run them with works great and has a lot of folks on the forum for help. And http://www.homeshopcnc.com/LinearGuide2.html has some good prices on rails and ball screws.
Jimmy
Jimmy