Surely thats just a question of mining in much smaller parts, so that rewards are meaured in the Satoshis range instead of 25 whole coins. I think the harder but probably solveable problem if it was desired would be p2p traffic efficiency. I do think poolproof would be useful.
Well, the problem with "mini-mining" is variance, also known as "luck" [..] Miners want their payoff come in stable and predictable intervals
Thats because the minimum network accepted virtual "nugget gold weight" is too high for the end user miner. If the rate of average production for a spec of virtual gold dust was 1 second on a GPU (for some picosatoshi) the rate of progress would be smooooth, so its not the randomness per se, its the size of the minimum mining target. It'll be acceptably smooth even at 1 microcoin per hour for 500MH miner at a given difficulty.
The problem and reason for big 25 coin blocks I think is p2p network scalability.
You can therefore think of pools like supernodes in a p2p network. They hand "shares" sized chunks of work, out effectively the microcoin challenge and smooth it out for you, and like supernodes in p2p networks in general, they help the network scalability. There is healthy competition amongst pools, and the barrier to entry is low.
In an idealized crypto currency you could argue it would be desirable to be able to mine picocoins directly with out pools. poolproof as you called it. But I think for now the people working on the code are having enough fun scaling for transaction volume etc with the current parameters absent some interesting new crypto to say allow secure offline combinable and splittable proofs of work.
Adam