Evaluations under FAR 8.4

I am in the process of drafting a solicitation for services, and I intend to solicit under FAR 8.4. The estimated value is $8 million over 5 years. My agency handbook requires the use of "strengths, weaknesses, significant weaknesses, and deficiencies" in the evaluation plan. I have always been taught that if it looks and smells like FAR 15, you will be held to FAR 15 standards, so I am hesitant to follow the handbook. It also states that the KO must make a statement regarding the relative importance of price to non-price factors (again, a requirement of FAR 15). Lastly, it states that the KO must state the relative importance of the evaluation factors.

I realize that this is an $8 million requirement, and I do intent to award best value through trade offs. Am I wrong in my belief that acquisitions under FAR 8.4 are not supposed to require formal source selection? Am I trying to over simplify the process?