Incentivizing voting has been a concern of mine as well. One way to create an interest in participation would be for delegates to set their own fees, and users would pay the fee of the delegate they vote for. The transaction would still be processed by the forging delegate, but the fees would be split at the end of the round according to how much the delegates are charging instead of evenly. I expect running a delegate will be more of part of marketing its main business, like a company putting its name on a stadium, than used as a source of income by itself. The point of DPoS is to minimize the cost of securing the network, not make money for the delegates.