All right. First, the Fly-spy is breaking rules. Body 1 means 1 slot to modify with. It has 4 slots worth of modifications. Chameleon Coating is 2, the other two are 1. That right there tells me you need to go back through and audit the drones, to make sure that not only are their modifications legal, but also that they aren't over their sensor capacity, and that all those autosofts aren't dropping their response. Remember, autosofts that come with the drone don't have to be paid for, but they still count against processor loads.
Second, Chameleon coating is great for visual scans. It does jack against other sensors, such as Ultrasound, or radar.
Third, chameleon coating does jack against keeping the drone from being hacked. And even if a hacker can't see it, it will turn up when they're doing a detect hidden node extended test.
Fourth, the only drone really capable of doing surveillance inside a building would be the Fly-spy, as even if the LEBD-1 can't be seen, that doesn't mean it doesn't make noise or that people won't walk into it.
Fifth, Chameleon Coating does jack against spirits and astral observers. There goes that whole 'surprise' thing.
Sixth, Jamming/interference. Try getting a satellite link from inside that underground bunker, in the middle of that jamming field, or inside the shielded research area.
Seventh, physical illusion spells. If you can't think of ways to have fun with illusions, then you've never hidden a pit trap filled with spikes and acid under an illusion of a floor before.
Eighth, Countersurveillance drones. You know those nice powerful satellite uplinks? Other things can detect them too. See how those drones like a dragonfly swarm.
Ninth, backtracing. So the Yakuza have a hacker. He noticed a drone nearby, watching their warehouse. He hacks in, and tracks the signal back to the source, before uploading malware, and informing his buddies of an annoying person who ought to be paid a visit, if he doesn't just Black Hammer them.
Tenth, MAD scanners. Metal drones set them off nicely.
I can think of more, but that should be enough to get you started.