1) The point of Bitcoin is to be a global currency, it doesn't make sense to use Bitcoin as a replacement for a national currency
2) Block chain checkpoints are already done at each release of the client software
3) To generate a longer chain from scratch doesn't require more power (CPU time) then the network currently has, it requires more power then the network has put into the chain since the start. The current chain has had unbelievable amounts of CPU time go into generating it.