Interesting problem. That is a huge plate. If you make it of plywood, you can cut a rabbit so you have just shy of a 3/8ths lip. Then you can use some Kreg levelers to align the top.
A much easier solution would be to lay a double sheet of Baltic Birch ply (flat as you can get) Half inch on top, 3/4 underneath. Order any aluminum or phenolic plate, everyone makes one for the 1617. Before gluing the two pieces together, cut the opening for the plate in the half inch piece. You want it just a hair larger than the plate for easy removal. To minimize tearout with the jig saw, drill four corner holes (same size bit as the curved corners of the plate). Put tape on the top so your cut won't be so ragged.
Line up the two pieces and draw a second cut line in the thicker piece so it leaves a half inch lip all round. Carefully glue the two pieces together so the openings line up properly. Add the Kreg levellers, then using holes in the table, screw the ply top to the table.
I would wax the heck on the top using pure past wax (Johnson's). Polish it thoroughly. This will make things slide even better. I wouldn't screw then insert down, the weight of the router will hold it down, and it will be far easier to lift out that way.
Given you are single handing this rig, I think I'd drill a large diameter hole an inch or so from a corner large enough so you can use a finger to lift it out. If you use an aluminum plate, use a rat tail file to smooth out the edge of that finger hole. And I strongly suggest you buy a plate with a twist lock (bayonet style) insert setup. The type with screws is a PITA and the screws always fall somewhere out of reach.
PIx 1 is of the Kreg Levelers, Pix 2 is of my favorite plate by Woodpecker. Expensive, but 3/8ths thick and twist lock inserts, but I have a heavier router in my table.
Hope this helps. I tried to keep tools required to a minimum.
BTW, if you are in a wheel chair, consider making a U shaped stand for the top. It can even fold in, kind of like those project displays kids use, but of ply and some 2x to stiffen the edge. HD ply will do, and have them pre cut it. That way you can pull your chair close. There will be a LOT of sawdust under the table, so you might want to make the stand so you can put a narrow trash can under the router.
Geeze, one more thing. You can get a base that will let you set the bit height from above of the table. I just searched for that key, and it found for $57 on Amazon. See third picture.
Bosch Under-Table Router Base with Above-Table Hex Key RA1165
Bosch Under-Table Router Base with Above-Table Hex Key RA1165 - Router Accessories - Amazon.com
I also suggest for anyone, that you buy the smaller model of the Grripper, to feed your work through all the sharp spinning things. It is the number one safety item in my book, but I think in your case, it would be on my must list.
If you have drill bits and a jig saw, this top won't cost anything like a chunk of aluminum plate. Try Kreg, or any of the other woodworking outlets and makers for an aluminum plate. Should get this done for around $50 to $60 bucks, less if you make a plywood mounting plate.
Some folks around here just drill a hole in the top layer big enough for a good size bit (1.5 inches or so) and are happy with it. But that means bolting the router in place, which I think would be a genuine pain.
Hope you find this helpful and practical.