Surprised this hasn't been made before, created a patch for the incest and walkthrough mod to work together. It's just a simple copy-replace of the walkthrough tags into the incest mod files. Didn't test much, shouldn't cause any issues on paper.
Install both mods then replace all five files in the game folder.
Not completely sure if it will work 100%, as I change a bit the code, and even more, the text from the one of the original software, but cool if it does.
The doubts are because you are talking about doing a copy-paste and automatic replace to add up the walkthrough tags in the incest patch, but my file is modified by hand, and there are a couple of differences in code, so it is not really identical to the one from Zorlun, although it does not change the overall story (because it is Zorlun's story).
One correction though, you are wrong in saying nobody tried to mix them, if I remember well, it is
Jellyluve who has been making a combined walkthrough+incest patch mod - but to do that he had to eliminate some parts of the incest patch, exactly because the code does not match 100%.
So, if you find a way to make them work together and are willing to continue it, as far as I am concerned, you are very welcome to do so- just double check, specifically, one scene with Dr Silver, is where there is the biggest code difference, I had to add up choice to the menu.