Let me help re-structure your question.
While the thought of trading McCoy sounds outlandish, the concept of a player-for-player trade or a Player+pick = Sherman may not be a bad discussion to have. What would the Bills give up to bring an aggressive DB into the fold ? Against Brady (with Cooks) on the other side, an strong secondary would be a good strategy. What other chips are we willing to use to sweeten the pot ? Wood ? Clay ?
In any case, this discussion should be merged in the larger Sherman thread.