Here are the 3 UI mods that have been argued as necessary for decent play:
Additional Camera Stuff - for build range rings showing up, this is planned on being integrated. Carries a bunch of superfluous camera hotkeys that some people use but tons of people don't.
Advanced Target Priorities - gives you additional control over unit targeting. Was partially integrated as it was deemed too complicated and too much information for new players to be given which would only harm them in figuring out what they need to focus on to actually get better. A simple version with ACU and unit priority was integrated and once they reach intermediate level on FAF they can download the mod to get further control when that gives them greater value.
Supreme Scoreboard - important tool for replay analysis, was not integrated because it harms performance compared to normal scoreboard which can have bad results for many FAF players with poor PCs that weren't intending to "get good" in the first place. Left as a mod to better accommodate this reality.
Banning and integrating these 3 carry their own issues and disregarding that for some weird puritanical values that don't actually impact the high level scene nor solve any actual problems is such a waste of time.
Another fun thing to imagine: you have now destroyed all icon mods people have developed and mandate everyone to play with default icons. How do you think this will impact the guys playing on like 3440x1440 resolution or higher?
If the solution to all of this is "make a settings and option page that would make Dwarf Fortress blush" then you have now entered terrible ui design territory that scares away new players even more than some spook about "cheat mods" does.