I'm still mulling over design. The top is a 100 x 50 cm x 22 mm sheet of hardwood ply with an alu plate set into it, but beyond that I haven't quite decided how to mount it. I can either (1) screw it on top of one of my benches with the router hanging down in front and one of the face vices wound all the way out to support one side of the overhang, and maybe another leg to hold up the other, or (2) I can hinge it onto the front of the trolley I built a couple of years ago to accommodate my bench sanders.
1) is simple and fast, and puts it within easy reach of the dust extraction hose, but means that the drawer under the bench, which holds sundry drawing kit, calculator and a few other useful odds & sods, will be inaccessible while it's mounted.
2) is harder. It needs two relatively sturdy hinged legs that will fold away when the table is collapsed but will lock firmly in place when it's in use. The advantage is that being already on castors I can put it anywhere in the workshop, and even use the sanders with the router deployed. The disadvantages are that getting the extractor hose to it won't always be as easy, and while one of the sanders works beautifully with the extractor, the other one (belt) puts dust everywhere but the extractor port; so if I use it while the router table is folded down with the router in, the latter will be covered in dust, which could easily be metal. I'd probably need to enclose the router, or panel three sides of trolley, to protect it.
I'm leaning towards (2) just now - lockdown occupational therapy - but stock to make the legs is a bit of a problem: most of what I have is far too good and the rest is weird-shaped offcuts or MDF, which I hate. I don't have any of those locking arms you get on folding tables, either, short of cannibalizing something else.
@Ham, thanks for the suggestion. I was looking at the Triton table too, but I rather overstretched the tool budget in the last couple of years and MrsT's eyebrows are very expressive.