It seems that everything you proposed looks okay to me. There is only one thing. As Patrick stated in his question number four.
Should font and color influence latex_renderer? Latex support colors of text and different fonts. Implementing this would be additional job.
Maybe is best to enable text coloring, just adding /usepackage { color } and if user want he just add inline coloring with \textcolor{define-color}{text} or any inline text coloring.
So this part is maybe problematic. Should set_font and set_color be implemented and never used or how this should be handled