Secondly maybe you could booby trap the bike. Like say get a different seat that if someone sits on it they will get nails up their ass or something. Thats just me though.
Or maybe the old spark plug lead in the gas tank trick so when they try to start it and steal it it blows them to smitherines 
That sounds like a "Man Trap," which as far as I know, is illegal everywhere. So is protecting property with deadly force except in Texas
at night, I am told.
Frustrating, ain't it? Especially when you realize that while you get some $$$ back from the insurance company, they get it back from you over time anyhow in the form of increased rates. If not for you specifically, then from all the folks in your area, as it drifts toward becoming a high-risk neighborhood.
Had a tricked-out road bicycle swiped off my porch one time, so I know how you feel. But all you can do is report it and see if you can get a plate number (which is probably stolen anyhow) or some kind of description next time around... without endangering yourself or using deadly force improperly.
One thing to remember is that these "gangs," if that's what they are, do come back at you if they know you have identified them personally, or are going to testify. And they know where you live. Let the police handle it. If they get caught because the police nailed them at a chop shop or whatever with normal police procedures, then you had nothing directly to do with their getting caught.
Terry