Basically this. If you understand how pure corner commutators work at all, it should make sense. It's hard to visually track 3 random corners in the middle of a partially solved cube, so cubers are allowed extra stickers for the official event, that they then number, so that the numbers stand out when going back over the solution. You just apply them on top of the sticker that needs to be swapped to a different sticker, and so on. You only need 1 2 and 3 (since the commutators basically only ever swap 3 corners), so the way I would imagine you guys doing it would be printing off labeled stickers that say 1, 2 and 3, maybe 3 rows of that for one sticker sheet at a total of 9 stickers. These would be smaller stickers preferably (42mm?) so that you could still see the color of the sticker that you put the numbered sticker on for normal 50-57 mm standard sized cubes.
Alternatively, you could do these like you do the custom logos, and make them transparent so that just the numbers would be visible
The biggest problem as to whether you could do it or not would be how re-usable the stickers are, since they would be taken on and off many times for FMC solves, probably twice or so per attempt. i would imagine it's easier to do this with the transparent material? but who knows