Perhaps you could change the properties of the flash bang and turn it into a weapon, also I don't belive that they had knives so maybe a vibroblade. (Yahoo, vibroblade combat!)
Maybe you could also add in a capture(or kill) the commander. Maybe like capture the flag with a flag that can kill you.

No way. And theres a good reason why:

Kidnapping - it happens already in BF2, you keep reviving someone and killing them (takes 2 or more people), forcing him to leave the server. With stun, you can just keep stunning them without ever killing them. They're helpless.

Another way to do this would be (in fact you could be doing this already) to give both teams stun batons instead of knives (I believe the rebs had knives before); and the advatage of creeping up behind someone is that you can stun them (with the effects above). Of course, when you stun them, you get a dog-tag saying "Player X got stunned!" which you can proudly display on a forum. Once they're stunned, you're free to kill them. This would be useful if you sneak up on groups. You could stun one and shoot the other, then reload and shott the stunned guy.

I think I'm missing something. That would effetively just be a short range version of what Arc is suggesting above. How would that stop someone from "Kidnapping" as your putting it?