I think preventing large stakeholders from being able to "win" easily is much less critical than making sure they only win when the whole community wins. A longer vesting schedule might help with that, and I favor curation penalties as well so that regularly voting against strong stakeholder quality consensus has a cost.
Whether people mainly vote for quality or just to reward themselves will determine whether Steem devolves into a Ponzi scheme or not, and I see that as the largest risk for the network.
Once too much stake is held by abusive voters, the only way to recover will be forking them out. The sooner we can stop abuse from being profitable the less likely that is to be necessary.