Just going to bump this because I'd really appreciate seeing this implemented.

I hadn't seen this thread before and I know this isn't the best solution; perhaps you can create a "viewing" box using the Elsweyr gates so that only you and decorators can get into the lever area.

In addition instead of using the gates you can just use actual walls, decorators can "move" the wall when they want to get in during the moving process the wall isn't counted as there so they can walk through but no one else can. Then they cancel the action and wallah no one can get in but those who are supposed to have permission.

Sorry ZOS hasn't considered this change already but I figured I'd provide some workarounds if you hadn't already put some in place.

Here's the problem with using walls or other "solid" items to cage in the switches. They aren't really solid. I'll explain.

A friend of mine wanted to host a dueling tournament at his house. He wanted the duelers to be required to stay inside an enclosed space and be penalized if they left the specified area. We decided that was unfair without physical barriers at the sides of the dueling space. A person shouldn't be penalized if a skill of their opponent's knocked them out of the dueling area. (A skill like the Templar's javelin, for example)

We crafted several of everything we were capable of to test it. Wooden walls, stone walls, Gates, etc. We set these things up to test and proceeded to duel. And every time someone was knocked toward a supposedly solid barrier, they passed right through it as though it wasn't there.

You say you host fight club and want to keep people from messing with your switches. Whatever you put around them as barriers, people will be getting knocked into the area through whatever walls you put up by the actions of other players while dueling.

Why not make an announcement at the beginning of the event? "Please do not mess with my switches!" If people you are inviting into your home don't follow your rules, they shouldn't be invited back. Even in a game.

Indeed.
The usage of the switches should be restricted in the housing permissions.
As a temporary fix you can block the way near the switches(i.e block the way by a wall/cages/platform etc.).

I actually disagree with having the switches set to the same permissions as lights and other interactive objects.

I want to be able to set visitor permissions so that people can't turn off fountains and lights and gates in the house without losing the core feature of the coliseum, being the use of the switches

I gotta agree that the fact that people can get knocked back into furnishings, and that you can't properly duel on top of furnishings as platforms, is a big obstacle to decorating the house. I had to leave some knockback-into-able furnishings in place because getting rid of them would sacrifice too much of the house