HELP: Program/Plan/Campaign Folder Structure

Struggling to define a strategy for folder naming and structure.  We are a multi-product/brand enterprise, somewhat siloed (much to my dismay).  We are used to folder structures that originate at the product/brand level.  However, have been advised to set up hierarchy at the Date/Year or "Category" (Subscribe, Lead Gen, etc.)  level. Having trouble wrapping my head around this.

Questions:

1. Do you manage campaign for a multi-product enterprise or for a portfolio of offerings?
2. Do multiple people own workflows and processes across products/brands?  (want to manage admin and access rights closely and eliminate room for error of product delivering marketing and data/recipients used)
3. If so, what are key dependencies you considered when choosing a folder strategy?  For example, how connected are folders and data?  What other dependencies might there be that we might not be aware of?  In thinking beyond product silos, what structure have you had success managing?

Thanks in advance for your help!