P2POOL PPLNS Possible Modification

The P2POOL PPLNS (Pay per Last N Shares) system is really nice..

Am I right in thinking Miners CAN, if they want, make their block target even harder, thus finding less blocks, but get rewarded correctly given their hash power. They would do this to allow more miners to get on the chain, which is better for the health of the system.

The reason most don't do this is that the VARIANCE of when they get payed goes up, but they still only make the same amount as if they hadn't gone for the harder block.

So - 2 blocks at difficulty 1, say, reap the same rewards as 1 block at difficulty 2. ?

What I was thinking, was what if you paid MORE proportionally to a miner that goes for a harder block ?

So what if you pay a miner an extra percentage for accepting the higher variance. And not a tiny amount, an amount that would make the miner DEFINITELY go for it.

Say if you go for a 1000 times harder block, you get 100% more ? (That would be the limit, there would be no point going for an even harder block as the reward would only be 100%)

So that 1000 blocks at difficulty 1, pays X.
1 Block at 1000, pays 2X.

If you went for a 500 times harder block you would only make 50% more.. etc..

This would mean that more miners would be able to find blocks, and the successful miner would have to go for the Harder blocks as they make more money.

The truly successful miner would find 1 block in every PPLNS group, but as hard a block as possible. Thus maximising revenue and always being paid.

Would this work ? (Or is this implemented already somewhere ? )