Multifunction integrated BC/wetsuit:
-integrated, personally-formed backplate for tank attach
-solar panels on suit/tank that store up battery power for guages, lights, etc. (improbable, as would still require battery backup or precharge for cloudy days and deep dives)
-distributed air 'bladders' or channels along back, back of legs, buttocks with sufficient flowthrough to allow reorientation underwater, and unobtrusive 'purge' or exhaust valves for adjustment at any position as well. Ditto formed pockets for weights in better distributed locations (chest, waist, etc.). Distribute these as some sort of microcapilary layer in an engineered material and the buoyancy compensation can even become part of your thermal insulation (although the aforementioned flowthrough becomes an issue...)
-luminescent stripes for buddy vis and better deep vis (light-storing like the tritium or whatnot used in watch dials? electroluminescent with a small battery? bioluminescent sealife traps?
-surface roughness/abrasion protection like shark skin. Better hydrodynamics in current conditions yet also better skin protection for wreck penetrations or commercial diver hazard conditions
A 'conformal' tank. I know something cylindrical is the best for resisting internal pressure (actually a sphere would be even better, but worse ergonomically), but why not more of a flattened 'elliptical' tank that doesn't stick out from the back as much and streamlines the diver's profile when seen from the head down toward the feet? (Like a 'fat' boogie board shape sort of.) Something a bit wider might allow for off-center placement of regulator valves more off the shoulder thus closer to the mouth (shorter hoses, less tangle, less 'mouthpiece tug').
Internal tank pressure guage that wirelessly connects to a console. (Getting signal out of a metal tank might take some creativity). No additional regulator fitting or hose for guage purposes. I know they have wireless air-integrated computer transmitters now, but these attach to the reg and are external.
Some sort of integrated 'vampire guage' for current blood gas sampling - I'm imagining a wrist computer that samples through a microtubule somehow like a diabetic's blood sugar monitor, but for O2 and N2 levels. Or maybe something can be done optically, like the blood gas monitors hospitals use that shine a light through your finger, somehow.
Heads-up-display mentioned before is great idea. Integrate a camera as well ("look and shoot") as informational guages like tank pressure, depth, temp, and computer warning/status displays. Maybe ability to vary the optical properties of the mask itself either passively or actively - enhance 'reds' at depth, add UV reactivity, convert darker a la sunglasses for very bright/shallow dives (or to block out welding arc light or buddy's careless halogen pointing...)
Some sort of truly comfortable and usable monofin that really makes the body more aquatic when in use, but can be 'snapped apart' and deformed for entry/egress (so legs separate and bend, but only when you want them to).