Question: Is a minyan required to wait at any point during tefillah for someone who is saying kaddish but who is not ready to say kaddish when the rest of the kehillah has already finished?

Answer: One of the most cardinal principles in Jewish synagogue life is the prohibition against tircha detzibura - causing hardship to the congregation.

The reason why Halakha ordains that we take out 2-3 Sifrei Torah when we read from different places is so as not to cause hardship to the congregation while rolling the Torah scroll from passage to passage. I would therefore say it is incumbent upon the individual saying kaddish to be attuned to and in sync with the normal rhythm of the congregation.

The one saying kaddish ought not expect the congregation to be in sync with him.