Yeah but your idea isn't RAW, its a variant way to handle COP.
With COP being as powerful as it is already do you really think anyone would try to improve upon it by adjudicating it in a manner not described in RAW? You would have to have one crazy DM (who's probably only doing it because it serves his interests more).
Actually, I would think that my interpretation is RAW. Since, by RAW, the answer IS correct, whether the DM can answer it at the moment is a metagame thing and isn't part of the equation.
So, if metagame constraints prevent RAW from being carried out, then a workaround to enforce how the spell works by RAW would apply.
In this case, I'm not saying that the character gets to retcon actions after the fact, the character would get to predefine two sets of actions based on a Yes or No answer and then play as if he took one set and retcon to the other set of actions if the answer indicates so. It's not like the character gains any new abilities, it's just the best approximation of a perfectly accurate future prediction.
EDIT:
For people implying that Vecna-Blooded or Mindblank can protect against COP... FYI, it can't protect against the more esoteric uses of COP.
Simply because COP can ask ANY question and get it answered. Direct questions against the character with divination immunity will fail. Hypothetical questions about imaginary universes will not. It's probably not something that will fly in a game though, unless your DM likes logic puzzles. (like me XD)
EDIT2:
Furthermore, Vecna-Blooded and/or Mindblank will not prevent the caster from telling there is some divination-blocking going on. Even in CO.
Questions like,
"Is there any information about threats that I will get in 24 hours of which I have not received information of in the last 1 hour?"
- If the divination immune character acts to do something involving you, then you will get information about him (if only that something attacked you)
- Said attack is not revealed by COP questions because that character is immune
- Thus, conditions set by the question is satisfied and it returns yes
- Further questions about when you will get the information can narrow down the time of the attack
Theoretical: you can technically probe for the information you will get in the future and it will only concern you and thus bypass all divination immunity. Just ask about things you will know in the future and poof.
- The answer, if true, but will "change" the future.
- If any other answer is given, the attacker will get to you, and thus you will know, making that answer false
- If the correct answer is given, you now know the information, making this self-fulfilling (and the attacker might/might not get to you)