Clever strategies and tactics can at best be dessert, not the main course.
On the other hand, although the various villains each harbored their own nefarious designs, having suffered enough from disunity in their dealings with Xu Qing, they decided to set down three fundamental rules upon deliberation.
As for whether to abide by the agreement or not, they would definitely need to play it by ear. Regardless of the final outcome, it's better to reach an agreement first.
If everyone ends up not keeping their word when the time comes, isn't it also a form of everyone keeping their word?
Unity in advance seems unachievable, but in retreat, perhaps there will be a tacit understanding after all.