Here's an interesting thing I've found. The RAW state that AI's with the drone quality can 'jump into' drones and vehicles of a particular type (aircraft, groundcraft, or watercraft, selected when the quality is selected). Where do walkers fit into this? Groundcraft, or something different? I suspect they are their own thing entirely (which is a big damn shame). However, later on in Data Trails (p.156, 'AI Vehicle Combat'), there's a line that says 'Only AI's with the Pilot Origins quality may use autosofts in place of active skills (probably not relevant for an AI in a Walker drone), , they also use their Depth in place of the Pilot rating of vehicles/drones they are running on.' I'm thinking that an AI with the Pilot Origins quality, regardless of what kind of vehicle/drone they're running on, can do this. Bit pricey in all honesty, and all but one part would be useless, but it's a way of getting that anthropoid drone with a pilot of 6.
Since anthropoid drones can wear armour like metahumans can (within reason - Juggernaughts aren't going to be using armoured vests), I would think that a Direktionssekretar drone with an armoured jacket is hardly stretching the rules. I'm not sure what the total armour soak would be, if the base armour counts on top of the armoured jacket, or it's just the best of the two. If it's the latter, then you can ditch armour and focus on other modifications.