Hey your futa idea wouldn't be bad idea for this game but...
I think King have one son and one son cursed even crazier would be cooler.
It could go both ways like King surviving and bad nobility cursing only living heir as female only way for nobility thrive and have heir would be blind sex.
Problem with female heir is that its already checkmate at that point if King is dead and prince is dead then another wannabe or other king could come and kill everyone under presumption peace was made. That why most princesses are married off so there are no loose ends.
The game was bit boring because you can only do 2 things and and all thing How does one learn skills during day, there should be means have more skills learned during day. Were forgetting not all skills aren't done same hour time. For twelve hours you assuming king would have time for one thing that is sword training, normally that is incorrect dueling/ way of sword or smith weapons would been better for future king to be learned.
Twelve hours more there too many questions, meeting with dignities would taken 3 hours. what time left walk around castle. Exercise, followed by Learning still be man of many skilled. 2 things, its not 2 only he be doing I would think it most likely be 8 things. Its your game, I can't brand your idea of making seem like he was man who easy to be killed. Some kings were great back in day.