Interesting concept, in fact, the wife being a garage sale junkie, drug me along one Saturday, and I found a neat little commercial example of the idea, it's built like that little clamp/sawhorse deal you can pick up in Big Lots, but has a slot for a circular saw and hole in the slot for mounting your router. It has a set of clamps to hold the saw in place and holes for mounting the router, as well as grooves for guides and such. I have a circular saw mounted and use it for a portable table saw, as the legs collapse and the unit folds down nicely to ride in the back of your pickup. The outfit is made by Black and Decker, and appears to be many years old but still in nice shape, even has a panic bar on the power switch that works great with the saw and I am sure would be fine with the router should I mount it.
Since the wife found me a small bench top router table I doubt I will ever use a router in this outfit, unless I need one that's more portable then the little Craftsman bench top.
I know neither will work as well as a cabinet mounted table like they use on Router
Workshop, (Love their stuff!) but will do till I have the time and energy to put one together (should my skill develop enough so I can do the job.)