Hey Luke,
Firstly, I hope you're well amidst the drama. I also hope it isn't too long until we meet in person again.
So much I could say around the whole affair but I'll stick to the key theme of your post. While I agree 100% that people should take personal responsibility of their tokens, a blockchain cannot be architected on this premise.
A DPoS blockchain should assume that people won't take personal responsibility for their tokens (and won't vote) unless incentivized to do so. As crude as the Steem hyperinflation was, it was at least an attempt to incentivize users to hold Steem in their own wallets (somewhat).
I'm certainly not suggesting hyperinflation is the answer, however, if the concern is with the concentration of tokens (and by proxy influence/ voting power) in Exchanges/ third party intermediaries, then solutions must be sought within the game theory of the protocol.
Else the assumption needs to be that centralized Exchanges will be large stakeholders (and key influencers) in any DPoS eco-system.
The Steem status quo, where there is this weird reliance on the benevolence of the largest stakeholders (whether the stake was obtained by ninja-mine or custodianship or bought OTC), is fundamentality flawed. As we know, DPoS is designed for the largest stakeholders to have the largest influence.
If anything, a DPoS system should incentivize active engagement (and vote participation) from its large (long term) stakeholders and their interests should be aligned with the Witness and wider community. Particularly if those stakeholders are Exchanges.
Steem should want as many of these Exchanges invested in Steem's success as possible. As we know Exchanges will play a key role in facilitating greater liquidity and adoption... at least until we get to the point where Decentralized Exchanges become the norm.
TLDR; if we want to mitigate against Exchange influence it must be done via incentives and protocol game theory rather than hoping for a change in people's outlook on life. Otherwise, Exchanges, as large token holders/ custodians should be incentivized to actively participate in voting to ensure their interests are aligned with the Witnesses/ larger community.
Nanzo