Documents to store e-mails, notebooks, notes, creator databases, contacts, etc.
Just imagine if one could save all kind of files and information to matters / sub-folders created under documents: It would make zoho basically a fully fledged enterprise content management.
E.g. as a consultant you have different folders in documents, one sub-folder for each of your clients. The issue with Zoho as is is that you cannot move e-mails to such a folder or save projects under the client's folder. Therefore, the information related to your client is still spread over several applications and you will have to seek for it by either using the very great search tool or going through the different applications.
If one could move whatever kind of content to Documents, you would have the perfect solution: Everything related to one client is stored in simply just one space on Zoho.
Alternative suggestion: What if Zoho could offer a Tag system one can use throughout all of Zoho's applications? A tagging approach where I define once my tags and then have them available in all other applications as well. E.g. one can define the tag "Birthday" in e-mail. As soon as defined I have it available as well in Docs or cretaor. Would result probably in the same benefits as above first suggestion...