There is one thing I think precludes a full-on armed conflict between the Typhon Pact and the nations allied through the Khitomer Accords: a lack of a strategic advantage. The Pact nations now all have cloaking devices (lets assume for the sake of argument that they're on par with the one aboard the Scimitar
) and presumably have access to thalaron weapons. The Federation and company have transphasic torpedoes (assuming of course they pack the same punch against other ships as they do against the Borg) and quantum slipstream drives. If either side makes an aggressive move, the other has an effective counter. If a Pact nation attacks an Accord world, then the Accord could have a small fleet use QSDs to pop into Pact territory, completely bypass their border defenses, and blow up every shipyard and base in sight with only a few shots. There's somewhat of a parallel to the M.A.D. doctrine; one wrong move and everybody's going to get hurt.