That might be why the A3’s sturdier. If you don’t mind the loss of detail you mentioned, might be worth it to check a few higher-grammage A4 leafs for the sake of easier scanning.
90 is the highest I found in supermarkets but I didn’t check art or printing shops, they may have sturdier leafs. And available in smaller stacks, so that you don’t end up with 499 leafs you don’t need if things don’t pan out…
Another reason might be that the bigger size means you more often/easily draw farther away from the edges. In my experience, rubbing an eraser towards a leaf from outside on the return moves was how I folded the leafs. And I remembered that I’d also become much more careful when I erase near the edges by the time I switched to 90 g/m².
Hope this is useful to you.