I believe the idea is to stay far out of harm's reach with your carrier, only sending out a disposable grid or carefully setting up a drone attack. Besides, it also would potentially catch people by surprise, without giving them a chance to mobilize.
Precisely the idea, surprise is important.
However, surprise is only an element when the speed to react is actually viable. With jump racks there's the problem of both timing and well.. time. It takes immense amounts of time to charge drives that aren't over sized and incredulously expensive. So having a cheap disposable unit using these would likely take several minutes to charge, hardly a surprise in any owned system with not-even-decent scanners going off. You'd know exactly where they are and could probably guess what a sizable number of ships waiting exactly xxx jump distance from your base are going to do. Even a single enemy @ said distance would likely be taken as a priority threat.
Then the other side is how does one prepare without proper advanced notice/information. So if you're going to have jump racks you're going to be vulnerable mid-jump before you've prepared to set them all up. <_< regular racks don't have this issue. A random patrol and oops bye bye racks. x)
200 drones jumping in isnt much
also they would have a time limit before jumping to the next location (witch would be random due to realignment)
200*80 mass drones = 16k mass of weaponry and heavy shielding. 200 is plenty of drones, if you feel otherwise mass load in 200 soul drones as pirates and watch the fireworks.
i'm sure you'll feel otherwise once you've done that.
Way I see it there's some pros and cons here that I'm weighing in on before I even try to delve into jump-racks.. again.
Pros:
-A small control/transport vessel could bring all the racks to bear with enough time, forgoing the need for large heavily armed carriers
-Absolutely massive hordes of drones could be launched into enemy territory with minimal if any risk
-Racks could be setup ahead of time to launch whenever someone enters a sector, this could be used as a trap or a defense
Cons:
-They have the whole aim issue
-Setup time both for the drives
and the positioning
-Ill prepared for random encounters, the group is highly vulnerable before launch
-If the attack fails you have no chance of recovery (shared with regular racks so it's not much of a con)
-You won't know if the attack fails until it's over.
Despite all the cons some of those pros are pretty hefty. Having the ability to launch many hundreds of drones suddenly with or without warning is still pretty awesome and can be game changing. Needing only to use a control vessel as opposed to a much larger and more expensive carrier is also highly attractive. A cheap control vessel is thusly a good way to save fleet resources that could be spent on more drones, or larger defensive cruisers.