It is interesting to me that this idea (maybe it needs a nifty name like 'sidechain' because bitcoin blockchain-distributed premine seems cumbersome!) and Sidechain is happening at the same time. I'm liking the sound of both atm.
Quick question: If in the event I've locked a chunk of bitcoins and transferred value into a sidechain alt, would I still be eligible for the whole of my bitcoin holding (including that locked up) or would I lose out from the currently unspendable bitcoins?
You would lose out unless the genesis of the new coin also recognized that particular sidechain keys. Depending on the details of how the two-way peg works, it might be possible to recognize keys from any sidechain that is exchangeable into btc.