You're welcome.

As for the robot stuff, people love plastics are armour at the moment. HDPE weighs 1/8th that of steel, so a combination of the potential thickness you can use and it's great impact resistance (plus the fact that at that width it can also be strutural) means it's very popular.
Ti is great, light and strong but expensive. And then people use wear resistant steels like Hardox for spinner proof armour, but hard to find and heavy.

As for drive transfer I believe lots of people use those chains, but nowadays people are edging towards timing pulleys and belts. They're lighter, don't stretch and don't come off. You can also get HDT belts if you're worried about them breaking.

That grabbing robot looks awesome!