For halo 5, i would like to see armor customization go further. each peice does a certain upgrade such as stranger damage, faster sprint, more shield, faster regen, regen shield, on top of what you already choose as your loadouts. (not saying a drastic change but you can stack to be just a bit more stronger then normal.) using weapons over time gives you available upgrades like being able to attach needler to another weapon or being able to put the magnum on a assualt rifle for added power. which would compliment the newly added armor customization.
For forge, being able to set terrain would be great. I think if you can make some crazy landscapes in a simply game like minecraft. Im sure it wouldnt burden you guys to give us more ability to build our own landscapes. More money or the ability get more items. Its horrible to get a good map going only to have to compromise using something else just to make a wall.(or be able to sacrifice a certain type if we dont use to give avail to other stuff we need)
Weapons like I said before being able to make the smaller guns to be attachments would be amazing.
If they upgrade kinect system would be a new lvl of fun to be able to play that way instead of using the controller. (plus if you guys would make a halo gun as a something we can actually hold with sensors that would be sick and make you guys even that much more money)
vehicles I think are great as you have them. Maybe if you added something that is an upgraded version of the mongoose that had say turrets on the sides and had a top cage to it like a go-cart (something like a ghost.) bring back the hornet!!!
If you guys made a map that was space or air revolved I think it would be fun. make the game type like capture the hill but only have to touch the spot that way it moves to a different area. Or make a map that is water based and make use of vehicles that could be driven on the water.
Armor abilities would be nice to be able to make upgradeable when you play the campaign on each level gives you peices that goes to your armor that can make your hologram appear to be shooting or your regen shield doesnt distort your vision, thruster has longer life span, promothean vision can send out in a short distance that disrupts shielding in half, the shield can be made 1 sided to allow shooting through with one hand (magnum or bolt (no charge)) adding teleportation would be crazy but i can only see that working like it does in the campaign, in short bursts so you can still follow where the person goes.
oh and put my face in the game as a character lol.
Thats about all i can say about that, lifes like a box of chocolate and all that good crap. Have a good one.