Probably you know about all examples of these sorts: https://steemit.com/steem/@heimindanger/don-t-use-vote-selling-bots-use-promoted-instead-a-bot-that-upvotes-you-when-you-burn-money#@napkin/re-napkin-re-gavvet-re-gtg-re-heimindanger-don-t-use-vote-selling-bots-use-promoted-instead-a-bot-that-upvotes-you-when-you-burn-money-20170712t210356197z

A blockchain is a software and mature softwares are not supposed to stay dumb. Automation over blockchain is very possible and some teams already combined it with high intelligence behaviors of machine learning. Something like that in my opinion should be the goal not adjusting the values of upvoting and down-voting times to times. It just doesn't work.