Since "big-list" questions are expected to get more than 30 answers, is it OK for you to remove the "This question has more than 30 answers" warning?
Could it also be done on other meta stackexchange subsites?
The notice is intended for future answerers to carefully check if what they plan to submit has already been posted. So all the more reason to have it implemented in big-list questions.
I'm not sure what you mean by whether it is OK for a user to remove the notice as it is a pop-up that is meant to be removed after reading it.