All in all, better to make an existing king a queen, or make an existing knight a lady (but with otherwise same plot and dialogue), if you feel it is necessary,

All in all, better to make an existing king a queen, or make an existing knight a lady (but with otherwise same plot and dialogue), if you feel it is necessary, than to take one of most carefully researched and written novels in history and just rewrite it. Or make a spin off story that focuses on the role of some overlooked women. Or better, a satire or a separate work that alludes to LotR as commentary.