Opinions please.

I'd like to hear opinions as to leaving open hooks on proposals.

Such as creating a unit that "can only attack flying units."
Or "This rule doesn't apply to players with invisibility."

Assuming flying units or invisibility aren't defined in the proposal(s) those are in. And that they aren't defined in and current rule when the proposals were proposed.

Are there any oppositions to leaving things like this to give other people inspiration to add things?