Lannister can easily crush Greyjoy, so I assume Greyjoy is not daft and will back off. In a 1 vs 1, Lannister would own Tyrell. Westerlands are pretty rich, and trade with Tully and Greyjoy will do wonders. Unless Tyrell makes peace.. But that's between you and the new Lannister. Remember Lannister starts with all of these forces and the books balanced.
















