Implied consent is certainly open to broad interpretation and is sometimes abused, but it is a concept that exists under most, if not all, privacy laws that I know of. It is a recognition of the fact that in today's technological environment, you cannot realistically ask people to consent explicitly to every use of information that will be made.
On the issue of what amendments to make to the consent regime, I would maintain my recommendation to align the language of proposed section 15—not subsection (5), but another provision—to the current section 6.1 of PIPEDA.