Okay, I've searched this topic, and found what seems like an answer. Problem is, I find it both too simple and too good to be true. So, just to check:

Let's say a character buys a Steel Lynx (large drone, Sensor 3). According to Arsenal, it should have the following sensors:

Atmosphere sensor
Camera x 2
Laser range finder x 2
Motion sensor x 2

And there's still room to throw in one more if I want.

Now, we want to improve the sensor rating. Only the cameras have ratings, so we simply buy two rating 6 cameras for 600 nuyen each, and presto! The lynx gets a sensor rating of 6!

Is it really that simple - and that cheap?

Of course, I don't really see the sense in having two of all of those on such a small drone, so I think I'll pull out the doubles and the atmospheric sensor in favour of a radar or something else. But it is still gold, right?

Yeah, and the fact that the Sensor rating gets added to the weapon combat skill for a "jumped in" rigger makes for a seemingly easy increase to the attack DP.

The 6 only counts for using the cameras, but since that's all you really want in most cases…

Quake, it's more like Sensor stands in for Agility (or Pilot, or Command). You're right that it may be easier to have Camera 6 than Command 6, but it's not really 'something for nothing'.

From what I remember, Sensors are averaged to produce the sensor rating. Well, at least every Sensor with a rating is averaged.

So, that Atmosphere Sensor that doesn't go over R3 will mess your average up, and, honestly, I don't think your drone needs to know what the weather is like. I'd probably suggest a Barometric sensor for a gunbot. It's got no rating, and serves the same function from the standpoint of ballistics calculation.

In RL cameras will be the way to go for positioning. Cheap, passive, useful for human operators. So it is appropiately cheap to walk the route of multiple cameras.

I´d add a microfone to get audio data, with SR sensor software it adds plenty of useful combat information.

Technically, SR cameras already have microphones (just as commlinks have both, by default). However, there don't seem to be any rules about the rating/capabilities of such 'built-in' bits, so they're best ignored.

On my spy drones, I'd always want a *laser* mic as well (in addition to cameras and microphones, that is).

I'm not sure if people usually use the rules, but the GM is also supposed to determine if a given test is hindered by inadequate sensor *coverage*. If you only splurged for a single camera, expect to miss things that someone with 3 won't.