You could do this in tiers where votes that meet a certain threshold require the additional check. For the whitelist, include an exclusivity clause that says if antiabuse certified bots are combined with non-certified bots, it results in whitelist removal. From there you can certify bloggers and give them a badge that states they are anti-abuse certified (which could give additional token awards). People wanting to maintain certification would be inclined to use certified bots, and non-certified bots would start experiencing additional pressure and could have their upvotes more easily directly targeted.