I think it can be pretty simple to begin with - announce that Airdrop #2 is incoming, and OP holders who vote for active delegates will qualify. The exact parameter for what qualifies as “active delegate” can be chosen just before the airdrop. Multipliers to those who were already voting before the announcement, of course. The question is how this can be executed - we need to work with the OF team?
Can think about more complex systems like you mention after that - it’ll be a challenge to make it happen without being gamed.