(Louis)

My view. Sorry for being late. :/
So i guess we are going non-gender for the time being? *shot*

Fire- Smaller-than-average build with a normal mechnical arm for his equipment, kinda like MegaMan with his X-Buster, cept with a robot arm in place of it. He can have a small tightened slingbag on his back and a tube is connected to the arm for fuel. The center of his arm can open up for the fuel/gas while he snaps his hands to create fire? Probably a REALLY young adult.

Water - Average build with slightly thinner proportions. She gets fin-like arms(like Batman's gauntlets. Water Blade?) that are connected to a slim backpack(to enable that 'flowing' shape).  Maybe add a diving helmet for those underwater adventures!

Electricity - I'll probably get killed for this. BIG build, something like Brick or Heavy, cept bigger. His entire upper body gets encased in some mechnical armour, and his face also gets a 'half-armour' thingy(like the Captain when he is Borg?).

Telekinesis - Average build, but has a slight hunchback to indicate his age. Gets a light armourplate for his body and dons cybernectic boots.