I might not have understood things fully, but I agree that it is an interesting proposition to have a smart ballot that allowed people to negate the opposite of a selected person's vote.
What happens if the 'opposite' isn't that clear?
What if there are more than 2 options for people to vote for?
I guess this is what you are discussing when you talking about the cardinality of active participants.
I would be interested to hear your view about my home country China. And how their selective democratic practices gave to their rise and perhaps soon, fall.. They select the candidate leaders for each region, and then allowing voting on those. This is basically what you're saying about voting for any colour car as long as it's black.