Ik this is already on the list of bug fixes, but I thought of a good way to fix mine carts and boats in spawn. You could just make it so when a boat or mine cart enters the spawn area it breaks. Currently it is still possible to get boats into spawn by driving them in, and mine carts won't be much different. If they both just broke the second they pass the border then you wouldn't need to prohibit them in any of the space shortly outside of spawn.
If that made sense cool, if not go eat some deritos.