Collections defined in the ROC or in a manifest preserve the orderings specified. However there is no way to specify an ordering on artifacts in an artifact package. Instead they appear to be grouped by definition name and then sorted by version number. Additionally the order in which they are displayed in the ROC varies in a non deterministic way.
It would be nice to be able to explicitly specify the order of artifacts of the same type in an artifact packages, rather then and for the artifacts to be listed in the same order as that in which they will be processed.