The default Service list field in PCF points to the workflow templates marked as "Shown PCF". Allowing a customer-workflow relationship so that only customer related workflow templates are seen in PCF (ie, customer X only seeing workflow templates associated to it) would allow a much better management of shared environments.
This would also imply that in the PM portal, when PMs apply a template they see initially just the workflows for the given client with a "SHow all" option.