I don't think PoW mining for ether makes any sense for generating ether. PoW was developed to consume resources for calculations to support their network. Ethereum is much more than a currency - so why are we going to use a system that consumes resources to generate ether, rather than reward people for giving their resources to Ethereum to support the more general purpose design? I'd like to propose the idea of following MaidSafe with their proof of resource system. It makes sense, don't you think?
I also like the idea of etherboxes - small, dedicated ASICs that do nothing but run contracts. Maybe a proof of work system could be developed based on running contracts rather than mining ethereum directly?
These are just some ideas I've had. I'd love to see what the community thinks!