I'd have some parts 3D printed, make some others on the lathe etc., some welding, some electronics, and build myself a temperature-controlled exoskeleton. Ever seen the movie 'predator' ? I'd come up with something like that. Only with the likes of peltier cooler units to serve as heat pumps, something like active camo, squid/octopus style. And perhaps some clever stuff with metamaterials to bend IR light, see if both IR and UV range could be bent and use electronic mini-screen VDU panels perhaps to do the optical range cloaking, power pack using supercapacitors perhaps for high density rapid charging energy storage coupled with batteries, or some of the newer hybrid supercap/batteries that are being worked on. The shoulder-mounted cannon, could go with an ETC (electrothermal-chemical) cannon or gauss weapon, the blades for the wrist would be easy to machine and laser-sharpened and electroplated with a layer of something like iridium to make them resistant to noxious corrosives. Rebreather, etc. I've actually got quite a few plans for such a thing up in my head. Done quite some research into metamaterials which can literally bend and weave light in various spectral ranges round an object or have it essentially refracted into a trap and dissipated. Something that could set the outside of the suit to external temperature so as to provide thermal imaging protection, optical setup in the headpiece for vision magnification in the IR and UV and optical ranges. wide-band and selective targeting modes for optional weapon systems. Extra fuel cells plus a leg-mounted holster for a coilpistol...
I really want to try finally making some decisions as to materials, getting the ones I can't fabricate made, like split-ring resonators if I couldn't manage a suitable nanofabrication process. Something to dampen ultrasonic imaging attempts...and of course, taking a little inspiration from the predator movies, both an arm-mounted field-medical kit plus autoinjector devices for well, whatever the suit would be set up to be able to select from for any given purpose. Various options ranging from antidotes, adrenalin, corticosteroids, sedatives, stimulants, agents for lowering body temperature, painkillers, something compact but widely functional.
Would be totally set. Able to walk about, seen or unseen as desired, and keep the inside of the suit at whatever temperature, programmed for whatever duration or response/change conditions I'd see fit. Some basic spectrophotometer type unit for chemical atmospheric and sample analysis (this has even been done before with an Iphone to run it and a diffraction-grating based on a piece of a CD-rom disk. And even things like regenerative braking for the down-stroke of steps, to conserve power. High density hydrogen fuel cells maybe. Solar cells as an option, have the camo on panels able to rotate round, so as to present alternatively, a solar collector power conservation system....even a military-style 'sniffer' (basically, the military of the US, and doubtless the russians, have 'sniffers' which continually sample and test the air for a preset range of toxic agents. I would of choice make my own choices as to what to look for, but basically have such a system designed to continually test the air, just like a snake's jacobsen organ and the microsecond it sniffed anything one would not wish to breathe, it would just trip the gas mask and set the headset to positive pressure mode if needs be.
Basically designed to deal with extremes of temperature, toxic environments, there would be increased strength from the electroactive polymer 'muscle' fiber bundles and cable tendons, all as lightweight as possible, using various polymers, bonded and unbonded carbon fiber in various places, as well as traditional kevlar/aramid-type fiber body armor and ceramic plate inserts, thixotropic gel armor additive layers etc. A spaced layer to defeat certain types of shaped charges and cope with moderate levels of explosive ammunition...(I'm not one to do things by halves), switchable optical and other EM spectral recording and auditory recording and playback....computer interface capacity would be good too.
When I see a problem, I tend to come up with a solution:P Lets just say I already have quite a few ideas of an environment-suit sort of thing way.
And if you think I'd be walking around in 40 'C, you got another thing coming darlin'. Fuck that in the ass with a pointy stick.
(yeah, I admit, I have put rather a lot of thought into the exact design parameters.)
All weapon systems based on electromagnetic principles and optical/sonic based options. Night vision, even ultrasonic echolocation translated into visual mapping. Passive and active IR/UV vision...designed for everything from comfort, to hostile environments, to strength in the physical sense, to medical treatment of trauma, to stealth and combat roles. (Why build multiple suits for multiple purposes when one could perform each task required of it, with a large range of capabilities?)