joeykrug and I have just implemented a proof-of-concept version of the "spin-off" idea discussed in this thread:
Website:
http://www.sidecoin.netSource:
https://github.com/AugurProject/SidecoinWhitepaper:
http://augur.link/sidecoin.pdf"Sidecoin" (our demo/example implementation) is a fork of Bitcoin 0.9.1. We modified it to support loading "snapshot" balances into the first (non-genesis) block, as well as trustless sidecoin claims using a new "claimtx" RPC command. Details are in the whitepaper!
Hope this can be useful to someone

- Jack