i think we are in agreement. to summarize:
we want the functional features (almost all of the process execution testing) to be tested in persistent as well as non persistent mode. non persistent mode is good for development of the feature. and it's also something we want to support.
the problem is that we want to avoid duplication of tests as much as possible if it is just doing the same thing except for persistence.
... is not really clear and needs further experience. we have some alternatives. we have to gain and share experiences on which tests should be developed like that and which not. and how the overall test suites will include the different kinds of tests.