Is it permissible for me to stipulate to my wife now that she cover her face and hands, after I have had a child with her, given that I did not stipulate this to her before marriage? And do I sin if she goes out with her face uncovered? And do I wrong her if I divorce her for this reason? And is marrying another woman who adheres to covering her face the solution?

The obligation for a woman to cover her face from non-mahram men, even when there is no fear of temptation, is a matter of scholarly disagreement. Our fatwa (religious ruling) is that it is obligatory. If you believe your wife is obligated to cover her face, then it is not permissible for you to allow her to go out with her face uncovered. A wife's obedience to her husband in what is lawful is obligatory. If your wife does not obey you in covering her face, then you should progressively employ means of reform with her: admonition, and if that does not work, then abandoning her in bed, and if that does not work, then non-injurious beating. If she does not obey you in covering her face from non-mahram men and you divorce her, you would not be unjust to her by doing so. As for marrying another woman, there is no objection to it, provided there is justice between the two wives. Marrying another woman might be beneficial in reforming the first wife, but this varies depending on the circumstances; it might not be beneficial, and it could even lead to greater harms.