The biggest problem here (which is why I'm not very good about keeping _oasis updated in general) is that baking the metadata into the archive leads to all sorts of duplication.  For instance, when the upper bounds change, we can't go back and correct the older oasis archives, so it'll get out of sync.  Similarly, the README has to contain this information, which then has to be duplicated into _oasis, which then has to be duplicated into OPAM :-/

I don't have a solution (yet), but just justifying my out-of-sync _oasis files for now