Actually, I can see how to pull off the "regular" pool on top of p2pool.  When p2pool mining, you must supply your BTC wallet address, and it must be valid.  If it isn't, your hash rate is directed towards the node's payout wallet.  Try it some time.  Start up your own node and connect to it with a user name of anything BUT a BTC address.

Now you just place a typical PPLNS framework on top of your node.  People register with a user name.  When they connect with that name, since it's not a BTC address, their hash rate gets added to the node's default address.  Now you have all of this hashing power on one address that is contributing to the share chain.  As soon as a block is found, that address is paid.  Then, you just divvy out the payment to the miners based on a standard PPLNS system.

So... I can see how it can be done, but it adds a centralized feeling to an inherently decentralized protocol.  In other words, for this magic to work, you simply cannot move from node to node as you can with a regular p2pool node.  The new node you move to / register with has no knowledge of any work you personally have contributed on another node.  Basically what I've described as a possible approach does nothing more than give people the ability to setup and run their own traditional pools using the p2pool network as a backend framework.  Sure, it solves the "small miner" issue, but at what cost?