I think there are some advantages to be had if some of the centralised pools would mine through a p2pool node, effectively creating a superpool.

Firstly, the resulting sharechain would provide an easy way for those parties with an interest in accepting low-confirmation transactions to know which transactions the pools are actively mining.

Secondly, if multiple pools point their hashpower at the same p2pool node, they will all see reduced earnings variance and get a share of the p2pool donations. This would remove (or at least drastically reduce) the incentive for miners to join the largest pool in order to reduce variance.

It would allow for much more accurate estimation of network hashpower and the hashpower split between pools (assuming pools don't hide their identities), which would also allow us to determine the fraction of the network in favour of a given proposal (think of the p2sh voting) more rapidly and accurately.