This is a all-terrain walker, standing on 6 legs, designed for exploration and mining. The "head" is articulated, where the 3 arms are operated. The crew is composed of the driver and two other astronauts, who seat in the body. Gull-wing doors open on each side of the walker. The two cylinders contains the ressources mined.
Love it! Love the colors, love the design, love the look... As for your leg problem, have you considered adding a few pins on the different parts of the legs and linking them with rubber bands? That might solidify the joins while keeping them flexible.
Although it has only six feet, it looks like a spider to me, with those thin legs. Very nice design, and very "classic" ! It could have been an official set back in the 1980s (and I'm pretty sure I would have asked my parents to buy it !).