You should understand that preventing sybil attacks is basically the core open problem in p2p network security research, and no one has any idea how to do it without either a centralized identity issuer, or via extremely wasteful constant resource-tests (as in bitcoin).
So there are 3 options:
1) Your scheme falls into one of two above: central identity issuer, or waste of resources.
2) Your scheme falls outside them and is totally broken.
3) Your scheme falls outside them and is correct. Congratulations, you should write it up, publish it in IPTPS, and collect the best paper award. Perhaps a PhD too.
I'm going a bit off-topic, but as long as we're here... Can you briefly describe where in this taxonomy fall
proof of stake ideas of myself et al (eg
this comment)? The general idea is to make sure that those with the ability to game the system are those with the least incentive to do so. The motivation is to enable high transaction security for those willing to wait long enough, with only a small amount of wasteful proof-of-work.