The ability to add custom modules and custom relationships between modules is what makes salesforce and SugarCRM so powerful. Zoho was great for us for about 8 months until we needed more than a very basic CRM. I think the CRM team need sto look at features like this, that make them able to compete with the big CRMs in scalability.
It seems like there is a pretty low cap on what companies can use a tool that is not more customizable (and that does not mean tryiong to fit my custom module needs into a tailoring of an un-used module -- that never works very well).
What would be beautiful, is to either be able to create a new generic module, or a new module of a specific type (opportunity, persone, etc) based on a template. I would even pay the zoho team to create a module for our installation.