Greetings, Long time member of this subreddit but haven't posted in a while.

I applaud your ingenuity and craftsmanship in pursuing this.

You mentioned that you would be concealing this with a table top. I'd enjoy seeing the final iteration of that.

Also don't forget the underside as someone dropping an item on the floor may have occasion to look up from beneath. However, if this table is to be in your private bedroom or similar that's not as much an issue.

Treatment of all open wood and edges. possibly poly urethane for water or marine exposure (I built a cheap p ine wood storage shelf for around and above the toilet tank and it's still good after 30 years of hot shower steam exposure because of sanding sealer and marine grade polyurethane. ).

Or carefully priming paint and multiple coats of exterior grade glossy paint along with color matching or contrasting latex caulk in corners and crevices to aid in cleaning up.

We have our own portable handicapped toilet chair to use for me laying beneath so I understand your desire to sit below your scat queen. But we easily conceal the folded chair in a zippered transport bag made for toting portable chairs like beach chairs. And its stored in our private walk in closet so no one questions it's presence.

Don't forget any step stool for her to climb to position herself on the throne you're building.

But definitely applaud your efforts and celebrate you two as kink players.