50% of the minting & tx fees for block N would have to go to a valid stamp for block (N-3). If there was more than 2 valid POS stamps (meets difficulty), then the strongest one would be used.
I highly doubt that will sit well with miners today.
I suppose the way the protocol would work is that 50% of the reward will be locked up, to be awarded 3 blocks later to whoever stamps the block.
Some downsides i see are:
- POS miners will lose the chance to mine transactions, which would have introduced much greater diversity in transaction selection (Increase censorship resistance)
- Block propagation advantage would be lost.
Upside is that POW hashrate is not reduced due to idle time.
No it is just POS validation of the POW chain. The purpose is to make it harder to do forks.
That is perhaps the most important goal of this scheme.
Hardening the blockchain would significantly increase the security of the blockchain and in turn greatly increase viability of Bitcoin being a long term Store of Value.