Only if you hold 51% of the total coin supply can you guarantee control of the delegates.
Other than this, it is just pure speculation. Your scenario where a whale may control 30 or maybe 40 percent of the total coin supply, and by plurality (or relative majority) they may take over the delegates is a possibility, but highly unlikely as he would have to create 101 personalities over night (unless he has been prepared for this in the past months and has created multiple identities). Although, how would this be beneficial for the whale? He would be sinking his own ship by the upcoming FUD and the possible demise of the cryptocurrency he is so invested in.
Explain to me how "personalities" are relevant to a block chain. A potential delegate simply registers a public key. They don't have to prove their identity in any other way.
Like you said, taking over all the delegates with a plurality of the vote is possible. So you agree with my core criticism of the security mechanism.
But I also think it is more likely than you make it out to be. Dominating the chain with a plurality of the vote is a way to optimize staking. A whale who takes this strategy need not intend to attack the chain or do any harm to it. But they will disproportionately be awarded new mint in the process. That's the underlying weakness and creates unreasonable opportunities and
incentive for centralization.