Multiple Award GSA BPAs Competitition

*Please excuse the typo in the heading.

I'd like to get peoples take on competition issues to the below situation:

Scenario:

Award multiple BPAs off of GSA schedules for project management training needs. You structure the BPA terms to cover the vendors entire GSA schedules. How do you deal with competition requirements if only 1 of the 3 vendors you have a BPA with offers the course? You are never going to have all 3 vendors offer all of the same training courses so how do you deal with competition in these type scenarios?