So I don’t think I’ll be able to get done with my chest and waist piece for my cosplay but would I be able to get away with having a cloak/cape on? Sorta like master chief had on in the halo 5 trailer.
Are you trying to enter into a costume contest? You can get away with a lot in a contest with confidence. I'm just wondering who you're trying to "get away with it" for? People are not going to make fun of you for having an unfinished costume just walking around the con. And if they do then they are jerks.
That said if you're just trying to pull it of better then I'd recommend bulking up under the cloak with a motorcycle chest or event rough foam to give the appearance of armor underneath.
That said... if it's not what you're going for then there will likely be tells. Chief in that ad made everyone question, why is he wearing that cloak? The consensus, the sand probably was eroding away cracks in his armor. So having the cloak without sand weathering might look off.
Long story short. Yes, a cloak will look better than no armor at all. But, part of cosplay is confidence and character. If you give it a reason and sell it, we'll likely believe you. Whatever you do, you have to do it for yourself first.