All of that is potentially an excuse for why, after you do it, it could be accepted by people as an explanation. Why weird things/actions can be explained. ((Although I'd argue that our straightforwardness and stuff, in our dealings with the Dwarfs, has been why they have been on good relationships with us. Not-acting-like-a-shady-Grey-Wizard, when we give our reports and talk to them, is one reason we've been doing well. Ergo, falling onto the "expected habits of a sneaky spy" suddenly is... eh.))
And anyway. None of that, however, is a reason to do it.
You've explained how we can successfully make excuses for the action, and blame it on Grey Wizard-ness. (Though the more we invoke weird spy stuff, the more shifty we seem, so.) But why?
Also: still easier to tell Belegar first, before the Council, and then see if we need to keep any of that shit back.
Rather than going to the council and being mysterious and mentioning that there's weird secrets to talk about.