Product Variant setting

Hi,

Why not simply set both images to both variants but set the one of the variant as main one (the first one) ? That way, by default you'll have both images but you'll see the first one as main and it will correspond to the preselected variant, and when you change, you'll see as main the other image of the variant you selected.
It looks the best to me.
If you set a "please select" variant, then yes, either you can add it to the cart, or not, and in that case you won't see the add to cart button unless you select another variant. There is no system in place to be able to keep the add to cart button displayed but have a warning when you click on it.