What? You had Triss for the whole time in The Witcher 1 and 2, how do you date to ask for more Triss?
What do first two games have to do with ignoring the endings of third one ? If this is a mod that is intended to be an epilogue to the Witcher
game series
* (which it does not really need, to be honest), perhaps it is not too unreasonable to expect it to take into account the possible endings, or at least those that are relevant to Geralt's fate ? That would definitely not be impossible, even if it would require more work.
In some sense, I think it is a good thing that there is no REDkit for The Witcher 3. In a game where the story and choices are very important (unlike in a "sandbox" game like Skyrim that is more about exploring the world and mostly unrelated mini-stories, and is thus ideal for quest mods), it is more of a problem when modders "censor" the original story by making changes to it or by trying to "canonize" choices they are pushing as the only right ones. If such mods became mainstream, all the biased and/or low quality fan fiction would be damaging to the original game and expansions that already include plenty of well made content.
I have to say, all this also makes me appreciate the efforts CDPR put into the writing and implementing choices and consequences in their games more. As much as they are criticized for various flaws, seeing others fail at it (or not even trying) makes is it more apparent how difficult it was to achieve what is in the Witcher trilogy.
* Edit: I would not really see a problem with this choice if the mod was written to be a continuation of only the books' story, or it was an adaptation of the short story
"Something Ends, Something Begins", but in any case it contained no references to anything from the games. What I do not like is creating a "sequel" to the games that advocates specific choices from them. A mod that is made for the purpose of pushing a "team" agenda or anything like that is not something I would want to support. It is a pity that this is what the modding community comes up with when it had the freedom to create interesting adventures with the tools that were released, but knowing what kinds of discussions dominated at the time when its development started, it is not too surprising.