Novama
Gaia let's us customize a number of things about the avi's body from the dressing room. I say if we want to get bigger boobs, then we should since it's an obvious feature of the body and no different from getting pointy ears or purple eyes.
no, it's quite different. those two you listed adjust features that have no impact on items equipped to your avatar. In fact, as a point, those ears you mentioned have a habit of clipping through items that fit tight to an avy's head, having random pointy bits stick out where they shouldn't. As has been said, they would need to rework ALL item's that go over the chest to also work with your shiny new ta-tas, and frankly, that's a LOT of items, not to mention variances between pose, etc.