I agree with you point that Anne feels that she will never be able to love either Charles M or Mr Elliot. Neither man "does it" for her, and Wentworth is a hard act to follow.

I also agree that JA felt that marriage without love to be morally wrong, and that the question is explicitly presented this way in MP. However, I'm not convinced that the question of a loveless marriage is explored in terms of a moral choice in Persuasion. Anne certainly has doubts about Mr Elliot's morality (Ch17: "How could it be ascertained that his mind was truly cleansed?"), and if asked she would probably say that a loveless marriage would not be a moral choice. But what I get from the text concerning Anne's main objection to Mr Elliot is the feeling that she could not depend on his sincerity. To put it simply, she does not trust him.