I don’t think it is about how hard to implement it is. The devs said that they want to be particularly careful with things that can negatively impact user experience and performance. Both of these could be impacted by these things.
You can already set up your loot filter in such a way that specific uniques are impacted by loot filter rules. (this way you can only show specific uniques you want or emasize/recolor them).
LP/Weaver’s Will is something the devs said they highly dislike adding, together with FP as well.