If mining is truely centralized the way you described it, the best option would be to decentralize or ban mining completely, otherwise the central forces will move to other things to centralize.

I'd prefer a situation where mining is suspended for the time being and maybe replaced with better alternatives. One of my favorite alternatives is rewarding the new miners with non-financial incentives like points/merits, ranking up in decentralized communities, more privileges etc. The rewards like points should only be used within the bitcoin communities.