I think these would be great to suggest as an enhancement request, but we do not currently have the ability to link things like KB/Question categories to Services, or any combination of those. An enhancement can be submitted from our Client Portal home page via the "Request a feature" button.
Only individual KB's can be linked to Services, but you can link to any number of things from the Service's details page via the description. That might be a way of accomplishing the relationships you desire until a built in feature would happen to be implemented.
Please let me know if you have any additional questions about this.