If you have a IC with drones since the IC is controlling them the drones use that persons BS instead of it's own. If they are controlled via drone controller, they use that model that is controlling it's BS instead of it's own. If more than one, use highest BS. P. 68
I'd probably use a HQ suit and bodyguards with drone controllers and drones as a example. All the drones if they were gun/missile drones would use the HQ's BS is how I read that.
As my understanding how would allocation works in 6th, if you have a Model with wounds that would instakill it, you can designate wounds on the shield drone. Such as 1 model, 2 shield drones (assuming your shield drones are in front). You have 4 instakill wounds. Designate them on 1 drone. Roll, if successful continue till fail, designate rest on the 2nd shield drone. It's like putting a terminator in front to soak up hits as a tactic I've been told people use a lot.
Though It's important as it's new that if the model controlling the drones dies the drones just don't disappear anymore. If a IC with drones joins a group and the IC dies the drones stay and cannot leave. If the IC is killed and not with a group and drones survive. Another IC can attach them to his group. I'm assuming he's within coherency to do so, but cannot take those drones into a group as they are not his P. 33. I assume the IC can still use them though.