That doesn't help much. You need to wait until your transaction is buried deep enough in the chain for an attacker with less than 50% of the network's computational power to be unable to reverse it. If there are many smaller, easier blocks, you'll just have to wait 300 confirmations (or whatever) until that target is reached. In other words, you always must wait for the network to do a lot of work after your transaction.

It would provide more fineness in desired confirmations; you could accept transactions with 2.5 Bitcoin-equivalent confirmations. But it's bad for scalability, and the increased fineness isn't valuable, IMO.