death penalty is just one of many possibilities in the concept in general. there are believe it or not people who wanted death penalty when talk of this mmo was in it's prime pre 1.0. but either way this thread isn't about death penalty it's about multiple server types.
The only extra server type there really needs to be is an RP server, which, as I mentioned before, the dev team is already considering. Have too many kinds of special servers and you just divide the playerbase, which is really not something the playerbase needs right now. If the game suddenly got really huge then I could see considering other kinds of special servers with special options, but right now its really not realistic.