Yes and I did.
Again: number of votes are irrelevant.

To do the same with 1 vote system, the attacker would need to buy 20x more stake.

Are you aware that you can't have 20x more stake than a half of the total? :-) No, that's not the solution, just a tip that your math is wrong.

It's a pointless discussion because you try to show a flaw, which is actually a property (% shares gives % of control). And yes, it's pretty much same with Cardano, etc.