I don't think they can mess them up for good without a good chunk of their forces lost, which they don't want that either. There's a reason they considered if it was worth it to make them a target of Kaido's wrath
In a war all sides suffer losses and obviously all sides prefer peaceful ways to avoid those losses.
But for WG having warlords+ yonkou system was basically because to have balance of power.
They cherish it so much that they immediately made Luffy a yonkou the moment kaido lost.
And, with all the resources WG has - Admirals, VA with potential VA who can be admirals+ FA + Seraphims + former navy veterans like Garp and Sengoku+ Gorosoi themselves and millions of soliers -----no yonkou crew is a match
Heck, whole purpose of luffy making allies and Grandfleet all over his journey is because he will be needing it to overcome WG