I thought of an extension, to put on my table saw---
after giving it lots of thought, evaluating the pros and cons,
I decided to go with a separate bench style router table.
With an extension on the table saw, I decided it would be to much of a hassle putting it up and taking it down, and resetting everything---
so I scrapped that idea.
With a separate bench style router table, I can leave it set up and tote it around to the job site.
You can make/buy a separate stand, to fasten the router table, to the top side---either bolt it or clamp it.
You can enclose the base, install shelve(s) and drawer(s), to store your router tools and associated accessories.
Works much better for me.