It seems that we can simplify package testing a great deal if we pull all the common manifest data into the package_data.xml and have package_data_<platform>.xml have only the platform-specific bits.
Currently, it looks like the platform specific manifest data is limited to:
|Status||Resolved [ 5 ]||Closed [ 6 ]|
|Workflow||no-reopen-closed, patch-avail [ 12653324 ]||patch-available, re-open possible [ 12665722 ]|
|Status||Patch Available [ 10002 ]||Resolved [ 5 ]|
|Resolution||Fixed [ 1 ]|
|Status||Open [ 1 ]||Patch Available [ 10002 ]|