I wouldn't mind a grapple hook, in say, an ODST type game, where you're limited in your physical abilities, but then again, you can have a limited jet pack for increased vertical movement.
The idea of grappling an enemy is cool, but gimmicky- again not to discredit the devs- and we've seen this back in CoD Infinite Warfare, Titanfall 2, and Doom Eternal, to name a few.
I think a revised, maybe toned down movement pool would suffice. A slower sprint speed for open map traversal, when vehicles aren't present, would be fine. Sliding into and out of cover is a useful mechanic and gives player options on how to tackle enemies. I love having options, as it gives you more ways to achieve a goal. Evade/thrust can be a useful tool for disengaging battles, or turning the tide on an opponent. Clamber, should map design allow for it, is very useful for vertical movement and can give you new vantage points to rain down holy hell-fire on your opponents.
Just refine what's already there, and you'll have a smooth, even gameplay that will do wonders for the arena shooter genre in the future.