I think reducing the pool fee by this amount and using the alt coins for a portion of management and Nasty Fans cut would be the best option. This encourages people to use the pool and would be the easiest to implement since you wouldn't need to convert as often.
I really like this idea! Server costs are fixed. Increased hashpower can bring more extra alt-coins. The extra alt-coins of 1 month can reduce the 3% pool fee for next month. If pool gets big enough the fee can disappear and alt-coins cover server costs and 0.9% to P2Pool development and 2.1% to nastyfans. And if pool gets even bigger with already 0% fees we could decide on what to do with "extra extra" alt-coins.