I think the most serious problem with the feats may be that GWM and PAM synergise so well. If these are supposed to model different fighting styles I think it's an oversight to let the polearm master also be a great weapon Master and add that +10 to the bonus action haft attack. Maybe GWM should have a specific list of weapons it applies to (greatsword, greataxe, greatclub and maul, I guess). Or maybe PAM should have some other way of using the bonus action that is, as someone suggested, more about control than damage. I'd suggest shove as a bonus action but shield master has already taken that. Would make more sense as a polearm thing to me but hey ho.