Honestly for as long as I can remember the event studs are a mad scramble for people worrying about unlocking them- so here's what i propose.

I know that personalized bars are a little iffy depending who you talk to but hear me out on this one, cause there's a few ways to do it.
Now the event studs are the maneaters who show up after X amount of humans are killed so wouldn't it make sense they'd visit individual territories based on how many humans you killed? So here's my ideas on how this could work.

X amount of humans killed over several days
This would have a personalized bar that carried over day to day, like after say... for a random example 300 humans killed, the studs would be open for you for the rest of the event, maybe have a cycle of studs it's goes through, or random appearance of which one showed up, changing on rollover.

X amount of humans.. per rollover
Let's say you have to kill 40 humans a day to unlock the maneaters, however it closes/resets on rollover.

X amount of humans, resetting stud
For this idea, let's say the number is 100 humans or something.
You can take your time filling up the bar, it carries over day to day, however once you unlock the Maneater, he'll be around for 2-3 rollovers (or the studs randomize during this time) then the bar resets and you'd have to re unlock it.

The reason I think the maneaters should be personalized is cause Some people don't concern themselves with them cause they want the DB encounters instead, or karma, so having to factor in people who don't care for them makes them taxing to unlock. This would make it easier for people who really want them to be able to get them.

Also this kinda opens up some new possibilities. like if they add randomized studs, there could be a rare one that might show up, or more special, etc.

So what do you guys think? Comments, critiques, and questions welcome.