Honestly, this sounds like a revolting idea at best - microwave pancakes - anyway, assuming you are determined to persevere...
Foil wouldn't work at all, ignoring the arcing problem. Foil is microwave impermeable, so it would just stay cold in the middle & burn on the outside.
I can't imagine the texture of microwaving pancake batter at a 'cake' thickness. I'm sure the outside is going to be like a car tyre by the time the inside is done, but really there's no way you are going to separate it into layers - it's simply far too runny. It would run round the edges of anything except rubber-sealed separators [which as far as I'm aware don't exist in a cooking context] & would soak into greaseproof sufficiently to still be a solid block by the end… but one with paper embedded in it at semi-regular intervals..
If you are still determined to do this in one block, then I'd do it in a rectangular container, and slice it like a loaf.
A late thought: Doing it in a single deep container, best be sure to put a lid on it. Heating a liquid which will turn to a solid in the microwave will generate hot-spots that will periodically go splut & redecorate the inside of the oven. If you get really unlucky & try to stir it every so often to redistribute the heat, Murphy's Law states that the first 'splut' will go up your arm ;)
Later thought: Buy ready-made pancakes from the supermarket. They will microwave just fine & already have a nice, pan-cooked look & feel to them. Not as good as making them yourself, but have got to be better than a solid block of unevenly nuked batter.