Hot take: No RDS instance should ever be part of a #cloudformation stack.
The technology is so immature that it is just a matter of time before the stack gets in an unrecoverable state.
Everyone knows this, this is why they suggest splitting stacks into persistent and ephemeral, but really listen to yourself. If it is too dangerous to put RDS into a stack that could need to be dropped, it shouldn't be in *any* stack.