I think yen fans are overreacting. They will never romance Triss and see this "awful lore breaking" content. Also it's not Triss exclusive, all their changes are for both Triss and Yen, with the exception of one scene (at the final battle) which was sorely lacking for Triss, and Yen already had one. Mostly it's just Triss haters that don't seem to like the fact that Triss is a valid choice.
Patching in shani was never realistic, that would have required huge changes, not to mention that she didn't fit anywhere into the story.
Triss already had a "about the future" scene (fountain).