This could work in most situations, as long as the pool is trustworthy. However, the whole notion of "relatively safe" 0-confirmation transactions can still be risky if there are any miners that want to be malicious. For example, if one was to accept such transactions, and someone wanting to exploit their trust by double spending and trying to mine their own block with only the second transaction. Even if 99% of the pools would confirm the transaction, the one that wouldn't could cause a lot of problems if exploited by malicious party. Combating such a rogue pool would also be hard if one wants to avoid forks in the blockchain (for example, by rejecting blocks without a given transactions).
In short, this approach offers slightly more security, if widely adopted it can work as intended, but it is not 100% attack-proof.