I had a few ideas for supporting ships that would act as force multipliers. It might be unbalanced depending on how the effects stack, but what about a frigate or cruiser module that would increase the targeting effectiveness against it’s target for all ships within a certain radius that are also targeting the same ship. It would work similar to how the target painter works, I’d assume.
Another support ship role could be a module to launch remote repair drones (possibly the size of fighters and could be shot down?) or shield rechargers/enhancers. If the engine would support it, you could even have a shield projector that would allow a ship to project a shield wall if kept in formation in front of your other ships.
As a support ship would intuitively give up some offensive power to supply this supporting role, the support modules could take up weapon slots rather than module slots to force the lower offensive capabilities.