I mean there are better tools, such as TMSU or tagfs, which i think are actually better approaches to having (part of) your file system displayed in a non-hierarchical way - or rather in a dynamic hierarchy.

But the other poster is also right in that for your system file system, i.e. root and operating-system critical paths, do not benefit from such an approach. I think asking for such a thing kind of sounds like an XY problem and requires listing the actual problems to solve with an alternative approach first.