Wouldn't it be sufficient to replace the PoW sheme with something far more complicated than SHA-256 to kick all the big ASIC-farms out? Just replacing SHA2 with something that can't be put onto an ASIC for years to come would be an easy solution to distribute mining again as the mining could be done by those running full nodes again. Mining wouldn't be a business anymore but more a compensation for running a full-node all the time.
If then some ASICs should show up in the future the PoW could be changed again. This also rather helps to secure the network in the long run as I just don't see how huge ASIC-Farms in third world countries providing more then 50% of hashing-power help secure BTC.