Probably the best way to decentralize POW at the moment is not to change the POW algorithm but to require multiple POW algorithms.

So for example one block can be from ASIC (current miners) and the other one from an algorithm that works well only with GPU.

We can also push this further by also having a third algorithm that works well only with CPU.

So for anyone to effectively 51{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} attack they will need 51{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} of the haspower on each one of the three algorithms.