How many multi-role support ships would a fleet need?

How many multi-role support ships would be needed for a credible fleet?

A pool around twelve could cover several support roles and keep multiple ships available through normal force-generation cycles.

The estimate builds from replacing Bay-class and Fort-class functions, hospital work, and Diligence-style support. A common pool lets ships rotate through refit, training, and deployments without every mission requiring its own tiny specialist fleet. A twelve-ship pool could keep several hulls forward while others train, refit, or prepare for deployment. Commonality therefore increases resilience as well as flexibility.