It is an option, but who do you trust to distribute the new genesis block?
The old blockchain itself?
- Calculate the resulting hash
- Make sure everybody is ok
- Hardcode the hash
Isn't this already done in bitcoin-qt? I'm pretty sure there are at least a couple block checkpoints hardcoded. Not sure why it still requires you to download blocks prior to that checkpoint. But to be honest, blockchain activity lately probably doubles every 90 days, so at most even if you did this every 90 days, you'd probably only save half the space.