The issue of compensating nodes needs to be addressed before placing an even much higher burden on them than they already have. And it goes up exponentially with block size, it's a P2P gossip protocol not "downloading websites" like Gavin used to say - which is moronic.
Actually, it IS "downloading websites". There are essentially 14 producers of block chain: the main pools. With them, you have more than 80-90% of the hash rate. If these pools are no idiots, they are linked amongst themselves by a high-speed back bone network in, preferably, if they don't trust one another, almost full mesh configuration. These 14 pools' data centres are the principal servers of block chain. They make the block chain and hence are the ones having it as primary source.
Any direct connection of your full node to one of their data centres (their powerful "node" that can probably handle hundreds of thousands of connections) gets the block chain directly. If you want to get the block chain through a P2P connection from another non-important node, you are just using that other node as a proxy server of the block chain, and not from the main servers (the 14 data centres).
I say 14, but in fact, 5 is enough: 5 miners have more than half of the hash rate, and they, for sure, are on a high speed backbone. It is in their interest to set up very strong nodes, so that the rest of the full nodes can connect directly to them, and not through a clumsy and slow P2P network.
So essentially, the mining pool concentration makes automatically from the bitcoin network:
1) 1 central back bone on which the principal miner pools are connected amongst themselves (from 5 to 14 say)
2) mostly direct server-client links to these 5 - 14 data centres by all "seriouis" client nodes, in order to get the most reliable block chain directly from the source as quickly as possible
3) at the periphery, small amateur nodes connecting in P2P mode to the serious client nodes, if they don't manage to go to one of the main servers.
Bitcoin's mining architecture does not favour a P2P network, it favors a central backbone + spokes network. Note that it is not a "single server" network: all important miner pools (5 - 14) are independent servers of the same block chain. You can connect your 'serious node" in P2P mode to several miner data centres in order to be sure that none of them is cheating on you and giving you a "retarded" block chain.
As the block chain is sort of "cryptographically signed" with proof of work, the fact that the source is centralized doesn't matter too much in its quality ; nobody can fake a block chain without spending huge amounts of wasted hash rate. The only thing that can happen is that you get a "late" block chain, but to avoid that, it is best to get it DIRECTLY from those that produce it: the main mining pool data centres, instead of letting it "drip through" the P2P network at snail pace.