Just be aware, Umaro likes to play fast and loose with the rules sometimes.
By RAW drones don't carry passengers making anything which adds them a non-standard modification (which means the GM might penalize speed and handling, vehicle signature, etc. for it)... yet he stuffs a rigger cocoon on one anyhow.
Many GM's will catch this and beat you silly for it... Use 2 slots to slip on a 'Special Storage' passenger compartment able to seat someone up to body 6 inside the drone. Then toss the rigger cocoon inside that. I've found they're much more amenable to that. (plus since you're inside the drone you get it's armor AND the cocoon).
Yeah Phoenix:...
the idea is to build a 'mini-tank' or 'mini-mech' and sorta go old-school... when riggers used to sit inside the vehicles they rigged. With large drones or small vehicles it's doable... The least controversial drones do this with are the large cargo/supply models like the auxila, or even the schildkrote since it has storage for hazardous materials. (you are hazardous aren't you?!

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The horseman is the absolute least controversial way to go about it. Since it's a small personal mobility vehicle designed to go inside buildings and carry a passenger.
My personal preference is the advanced cargo model. Any drones you have with you by the time you're in the building in a super slow walker drone should be capable of moving under their own power and should be launching from another vehicle like a bulldog (you're sure as hell not making a getaway in a walker mode horseman). With two full mechanical arms you can literally pick up and operate things like say an assault rifle (no need for a weapon mount). or if you can talk your GM into modifying the full mechanical arms with cyberguns and other cyberlimb accessories using capacity! (like say a cyberlimb gyro, cyberlimb SMG). (see mechanical arms/limbs mod).
p102: Mechanical Arms and Legs... jumped-in rigger... (one of their example skills is a personal combat non-rigger skill like blades!... why not pistols.. or automatics).
p139: at GM's discretion... full arms can be tricked out with accessories just like a full cyberlimb. (nothing says loving like a combat axe in the trunk and two arms with +7 strength augmentations... (strength == body of the vehicle)... so that's strength 13 total... meaning you're doing troll levels of damage with that toy.
But yeah with 6 mod slots... you're probably looking at either walker mode or smart wheels, hidden armor 10 or obvious armor 12. Cocoon. By that point you'll have used up 2-5 of the 6 mod slots.
Just be aware with walker mode... you're not going anywhere fast... especially after the 20% penalty to speed and acceleration for having more armor than your body score. (errata)