Given Charlotte's earlier views on marriage, what could her munificence in offering to entertain Mr. Collins foreshadow?

Charlotte's decision of marriage goes along with the pragmatic personality she has, shown by these elements that led her to the decision of accepting the proposal:

Firstly, because she understand the social status of her family is of a not very-wealthy one nor a very-poor, which is not attractive for men from higher or lower acquisition status. She can only marry a man from the same status, and Mr. Collins fits the criterion. Secondly, she considers that happiness in marriage is a matter of luck, not a basic principle of it. Thirdly, she knows that if she gets marry her sisters would be allow to find husband sooner than expected and that his brothers wouldn't have to worry financially for her. Fourthly, she thinks that marriage is only an honorable way for well-educated woman to get a small fortune, as she herself says.

Therefore, she doesn't care about Mr. Collins lack of sensibility or intelligence, because she sees in the proposal and in the marriage itself, an act of generosity for her whole family and for her. So, her acceptance is an offer of her life to entertain Mr. Collins, the only man (she thinks) that could fit her social criteria for marriage, and with that she allows her family to flow socially better. For that reason, all around Charlotte is happy about the proposal (except for Lizzy, of course).

So, the answer would be that Charlotte's munificence in accepting Mr. Collins proposal hides her pragmatic personality on marriage, more than anything in a society in which the role of all women is set in that union.

Charlotte's earlier views on marriage:

Charlotte marries Mr. Collins since his income is stable and he offers to have her own home. There is no space for true love from Charlotte since she does not believe that love is essential for a successful marriage.

Charlotte believes Marriage is just a business arrangement unlike Elizabeth who believes that marriage would provide her equality, partnership and mainly love. But Charlotte obsession over the business arrangement would be good for her for a certain period of time but in future when she thinks of getting engaged with Mr. Collins she will regret it and lead an unhappy life. She must be grateful to Mr. Collins for his generosity and character.