I'll preface this by saying that the reason I picked up Bio in the first place was the fact that it was a 120-line, simple and elegant solution. I'd hate for it to get too complex.
THAT SAID, the other reason I picked up Bio is that I'd like a lightweight CRM leveraging content types, node references, and Views. The short list of Bio's limitations to this end include: 1) field-level privacy, and 2) Non-user contacts.
Field level privacy is someone else's problem, but what about non-user contacts? I would like to propose a model where Bio nodes that are owned by uid 0 ( or perhaps some other predefined user ) can have multiple entries, and can possibly be matched against new users based on some criteria.