Any customer dealing with a ECM is accustomed to tailor the document space into folders and subfolders. In certain industries it's dictated by a standard -- e.g. in phrarma there is a notion of "drug dossier" presented by a folders tree comprising dozens of Word documents; the examples of folders are laboratary tests for durability or clinical tests in countries one, two, three...
Bizagi's approach is to store all documents of a certain type in one folder; documents belonging to all cases goes there. It totally shocks a prospective customer considering using Bizagi in connection with e.g. SharePoint or Documentum and makes the competing offering from the latter more appealing.
I believe it's relatively easy to remedy this deficiency: please add optional "Path expression" field that would allow to calculate the place to store a specific document within the connected ECM at the runtime. As a side effect, the missing (sub)folders should be created if another new field "Create missing folders" is set to true (default).