There's a mod one of my players has been begging me to use called something like "Unlimited Heightmap" which apparently removes that restriction. I've been leery of trying it, because it seems like something that can both easily be abused and possibly break games.

As for the "compromise" you mentioned, I'd certainly like at least a few more meters leeway. As it stands, it's typical to have roughly 10% (give or take) of copper nodes from a deposit hidden under the dig limit, and it would be useful to be able to get it all.

On the flip side, if they did loosen up restrictions, I can quite easily see myself dying liberally to fall damage in unfortunate and hilarious ways. (Well, more than I do already.)