Why don’t they seem plausible? What makes you think they have no place here?
As I said earlier U3 lacks good game mechanics and a solid progression system. On Vanilla you can have all items, a solid base, and everything else within a day. Even the quests that some maps offer only take up a couple hours.
U3 is a overly simple arcade shooter. After a day, that’s literally all there is to do. I’ve seen most people quit Vanilla within a few weeks because of this. Sure, the modding community has been adding plenty of cool stuff but U4 will be a new game without ready-to-use mods.
People simply won’t play U4 if it’s just a slightly upgraded version of U3. U4 needs to be more complex with more content, and this starts with better physics