Well, I used to build armor, as I said, complete with full flex riveted joints and all, the actual weight of such a suit is closer to 70 lbs max, usually less than that, closer to 50 lb, especially for a footman, most knights who wore the super heavy stuff only could because they were horseback, that and foot armor differed greatly. Jousting armor was not built for actual warfare but was a rich man's sport instead.
(added) Doing the internal framework is a whole year's worth of science project to begin with, as one of the earliest posters on this thread already pointed out. It would be an awesomely FUN Project, and one I would dearly love to play with myself, in fact. Even unpowered there are several obstacles to overcome, the degree of flexibility and the weight of the overall pieces. Spring-loading some portions of it can help to at least neutralize some of the weight, but may also restrict movement in difficult or awkward situations. Most of the ones that they have now will allow one to kneel, but going prone has it's difficulties and is slow compared to being able to throw one's self down into a ditch and crawl, presently they do well in helping carry extra ammo in and do well for 'mulework'. I have had ideas for the internal framework for decades, with refinements over time to match the changing and upgrading tech. I would happily correspond with you further. And I do not think that it would be illegal, just for a lot of us it would be cost prohibitive. I live on a very fixed income due to disability and only get $733/mo, but even when I was doing the Swords, Knives and Armor as a living, full time plus (doing up to 26 shows a year from knife shows to medieval recreation events) but even then I would always much, much prefer to work in steel as you can get the details easier since steel forms so much easier than aluminum does, even with just cold forming, heating is rarely required with sheet metal like that, if ye know what you are doing with a hammer. Of course, I tended to regrind the faces of my hammers and made a lot of my own stakes and forming faces, dishing stumps and the like so that I could get exact detail. An example:
An unfinished leg section, before full planishing and sanding work:https://scontent.fsnc1-1.fna.fbcdn.net/v/t1.0-9/1937103_1196935407410_393946_n.jpg?oh=ff6951c28da9b4a17ea3316522282236&oe=579F475B
Why I said that aluminum would be prohibitive is normally cost: The material cost and the extra equipment jigs and labor required. However if you have the money and expense is no problem, I would STILL say to go with the thin steel as it is actually lighter and stronger for the amount of work involved and is much MUCH easier to shape and bend and at least as strong as a finished product. Aluminum wants to crack while bending and it is very difficult to shape and unless you Really Know what you are doing, welding thin aluminum will be quite the trick ( I was a Navy Welder, I well know) and it is not at all like shaping steel or iron (especially from a blacksmith perspective). Steel can be easily dished with hammer, just like doing Body work for a car, but MOST folks have lost the techniques on how to do it smoothly. For much of the detail you will find it incredibly easier using light gauge steel sheet rather than trying for aluminum because while it is lighter, it is also a lot harder to work. I could teach you a lot about patterning and the forming processes for such a project, having built full suits of armor myself already and having a vast knowledge of the materials and how they may be formed, you would be vastly disappointed if you tried doing that type of forming, with any kind of detail, in aluminum and Titanium would be right out unless you had access to a full anaerobic casting facility. Believe me.
