If a Spirit Inhabits a drone, can the Pilot still control the drone? What if there's a Machine Sprite in the thing?

I'm having visions of modded-out soldier drones or tanks with Spirit buffed Body, Armor, and ItNW...

The way I'd rule it is that you just bought an expensive Plasteel Homonculus. The spirit is in control, fully. If the sprite isn't simply barred from working in the electronics then it's essentially in a commlink, unable to affect any part of the drone.

Thread-necromancy ahead!

I'm with Neraph on this one: You'll essentially have a weaker, more expensive Plasteel Homunculus.
On the flipside, the "drone" can now, as a living creature, be targeted by mana spells and does no longer apply its object resistance* to any attempt of the mage casting nice spells like "Invisibility" or "Physical Mask" on it. That can do a whole lot of goodness. My rigger has had a go at a normal drone with an invisibility spell on it (6 hits, awesome mage). It was glorious, the GM groaned. It gave us a real edge in combat.
*Remember though, the spirit in question will have to beat the object resistance first. A prepared vessel will add much needed bonus dice.

Another way of combining spirits and drones (I've mused over that question a long time) that'll work better:
Use physical spirit powers on the drone. "Movement" will turn any meek Manservant into a fast runner. "Concealment", if combined with chameleon coating, will make for a very hard-to-track drone. Just be careful of wards, as your drone has no way of detecting those.
Just mount that possession spirit of yours into a necklace around the drone's metal neck. In a pinch, if all goes south, it can still jump into the drone and go all Plasteel Homunculus on them.
Don't try and use an inhabitation spirit in that setup, it won't work.

nm

I wrote (sort-of) about this a while back:

Wireless Control of Spirits