A Body 1 drone can have Mechanical Arms with a Strength up to 10 (but it'll cost you out the wazoo, assuming you had enough Load to support the improvements) while Body 0 drones are limited to Strength 0. This would allow it to lift up to anything weighing less than a kilogram if you go by a really generous reading of the rules (since that would be rounded down to 0 kg, which is the limit for Strength 0).
All of the robots I saw above look like Body 1 drones to me. Body 0 ones are tiny little buggers that weigh next to nothing, whereas Body 1 are about the size of a typical RC toy. So it wouldn't be any trouble latching a Mechanical Arm that could give a troll a run for his money in an arm-wrestling competition to one of those.
But yeah, there's no problem slapping an arm on a walker drone. There's no standard anthroform chassis, but it wouldn't be hard to put one together. Just look at the difference in values between a Body 1 Walker and a Body 2 Walker then create a Body 1 Anthroform from the Body 2 Anthroform chassis following the same guidelines.
Although the rules only hint at it, there shouldn't be any problem adding an Autosoft Interpretation System to the drone and giving it a custom Karate Autosoft either.