Looking for an alternative lightswitch, push button maybe

I am going to mount a slate chalkboard on this rail. The slate is 60" which is the length of the rail as you see it.

As I get closer to the actual installation I am questioning my choice of dealing with the light switch. I was planning on cutting the slate to accommodate the toggle switch – cutting big enough holes that I could put the switch body on the front of the slate, with the plate over the top of it. The thing that is getting me nervous is that this requires removing a lot of material and I am concerned that this corner is going to break off when I drop the board into the rail.

The slate is estimated to weigh 65 lbs and dropping it into the slot is already going to be an adventure, I prefer to not have to worry about breaking this corner.

In terms of the holes I need to make, I am not concerned about precision. I will be able to make a perfect paper template to locate my holes exactly where I need them. For tools I have a set of diamond hole bits and I can handle an angle grinder.

The easiest thing that comes to my mind is drilling a little hole in the slate right where the switch pokes through (or two holes; to make one elongated hole) and use a toggle switch but that is going to look a bit strange because the switch won't stick out far enough to look normal.

Then I thought about those push-button dimmer switches – the ones that click for on/off and rotate for dim/bright. That one could be good because I can literally use whatever I want as the button.

I also thought about the old-school push-button because our house was built in like 1900-something and has a few of these these switches.

I am considering pulling the switch and covering the box; just using the pull cord on the ceiling fan. This is the way the house was wired when we got it. (Which is why you see the word BULB written on the wall – why do electricians think that's ok?)

But I thought I would ask you all if you have ideas.