Please spend time exploring the possibilities around this. I think there is a good opportunity to create a progression in the diplomatic game where certain agreements, diplomatic actions, etc. are not available until high enough level intel is available. Coupled with last week's updates to first contact, you could have something like this:
- No knowledge - First contact protocalls
- No intel - First contact war or peace
- Low intel - Conquer CB only; NAP agreements; direct resource trades/bribes
- Medium intel - Humiliate and subjugation CBs; defensive pacts; commerce/research agreements
- High intel - Form federation; other new interesting diplomatic options
As an above poster said, the game already has a big problem with too many "gamey" restrictions on what you are allowed to do. Your suggestion is terrible.
Games like this are always best when you are allowed to do whatever you want, but with consequences if you don't stick to the rules. For example, if we want to send our fleets into someone's territory despite closed borders, no invisible wall should prevent us from doing so. Instead, we should be punished diplomatically with reduced trust from every other empire, reduced diplomatic weight, and so on.