For the most part it's not that I can't complete a motion, it's more that I'd rather not do the repairs to the armour after doing the motion.
I can jog, jump and climb in my Spartan III but I know my limits and play within them. If there's difficult ground, I'll go around it. If there's puddles or wet surfaces I'll avoid them. Sometimes I just straight up remove the boots to walk around more freely. If I
needed to do certain things I could but I'm just lazy and will take the path of least resistance, especially when wandering around a convention or photo shoot location where having a piece blow out and delaying everyone else while I repair a part just feels rude and kind of embarrassing.
I can play "Head and Shoulders, Knees and Toes" in my suit but if anything falls to the ground I'll ask for assistance in picking it up because the Spartan diaper makes bending over a little awkward. Same goes for drinking from a full water bottle, I'll ask for help getting the first little bit because of the protrusion of the chest piece making the likelihood of spilling water all down the front and into an electronics panel a real possibility. I'm clumsy and I know I'd dump a bunch of water into my chest and short out something. The most awkward thing though is probably the gloves though. I wear mechanics gloves which allow some dexterity but certain objects can still be a pain to deal with. Before settling on a pair of gloves for your suit definitely play around with them on for a bit to see if you can do things like using your phone or getting cards out of your wallet.
I wore my ODST for the first time in a year and a half and noticed that I had none of the concerns that my Spartan suit has so I just derped around the Halo Museum with
Viper 466 at full tilt playing with everything. I'm not sure what suit you're planning
mumgoot but just know that different ones have slightly different points to look out for, especially in terms of field of vision.
Cosplay handlers are awesome and I highly recommend trooping in at least pairs for the awkward situations that will undoubtedly happen and having an extra set of hands is always great. And if your visibility out of your helmet is something limited like a Gungnir, having a handler act as a guide to find you paths through a crowded convention center isn't a bad idea either.
Okay, that tells me a lot. Right now I'm working on a Spartan build, and I was running into problems with pretty much everything. I'm doing it all super-quick and my main idea is to give me something to goof around in at local events/Halloween. The thighs and wrists look very blocky, and the thighs were smashing into each other. I might revisit those parts at some point, but I like how the chest is coming out. Even that has a few problems, but it's doable, mobility-wise. Therefore, I plan on fielding it as a casual sort of thing, just wearing the helmet, chest, and gloves. Other than that, just jeans and a shirt or whatever. Sort of like the male equivalent of the female mini-skirt spartans. 
