Please describe exactly what you see that is "chaotic" -- maybe include a screen shot.

Please describe how you want to classify your tags.

Are you wanting a hierarchical taxonomy system of labels and sub-labels? While that is theoretically possible (and there is very good, free software that can do that -- TemaTres, for example) integrating a thesaurus into Zotero would be an extraordinarily large task for developers and for users. It would involve several additional layers of complexity. For example, group members now have differing authority to add, edit, or delete Zotero records. With a tag taxonomy there would also need to be similar regulation of who can recommend new terms, place terms within the hierarchy, assign synonyms to existing terms, etc. Currently, tags are captured from databases and publishers and are added to a user's Zotero record in simple list format. Each of these sources have different terms for similar concepts. Each database will have its own, different, hierarchy with terms placed at different levels. Maintaining that kind of system, even with a moderate number of records and a very simple 2- or 3-level structure, will require users to spend a lot of time and with great attention to detail.

Thesaurus construction is something I love to do. What I would not want is to have responsibility to provide technical support for thousands of individuals who each have their own taxonomic requirements.

@adamsmith But we may be completely misunderstanding the question / request.

While the simple answer is "no"; I believe that a simple negative and a repeat of what Zotero can do but without an explanation of why doesn't completely answer a friendly question.