Just delete the hunts for centiruon seals or add other ways to get them

[Nestama]

the simplest solution in my opinion would be giving hunt bosses a 5-minute Invincibility buff, so no one can kill them, and would be killed instead if they start pulling early.

That would annoy certain servers, though. I think it's only the American servers where people wait, while the Japanese servers treat them as a first come first serve kind of thing (as SE intended).
What SE should do is never put gear upgrading stuff into Hunt content.