If drugstore giant CVS succeeds at merging with health insurance company Aetna, it would create an unusual consolidation of a health care provider and a payer. The billion deal ( billion including Aetna’s debt) is the latest move by CVS in its quest to become its customers’ “front door” for health care, as CEO Larry Merlo has said – but although there is a growing market for coordinated care, actually implementing such a system is complicated and would require the combined company to successfully upend traditional health care delivery formats. Moreover, the combined company may end up facing a formidable competitor — Amazon. In a news release, CVS describes the cash-and-stock deal as being all about integrating the work of doctors, pharmacists and other health care professionals “to create a platform that is easier to use and less expensive for consumers.” CVS and Aetna have combined annual revenues of about $240 billion.…