Just saw this post, may I express my idea about it.
IMHO xfProject file should be considered as the project metadata, containing all the items that are part of my project.
Adding a "*", would be an interesting opportunity but - at the same time - a big risk for the project integrity.
Let's say that we define a project adding "*" to get ALL the BRules. Let's say someone install in the same Application another project, with its own BRules that depends on their own Assembly.
Exporting the xfProject with the "*" would result in a mess, because I would get all my BRules (and that's ok) but also the "other" BRules... And the more projects (or customizations) I add to the application, the more mess I'm going to put in the exported xfProject.
A good alternative would be to specify the Items using the * syntax, for instance adding a prefix. So I would export all the BRules named "MYPRJ_*": that would select the rules, but it's not yet definitive, since I could end loading another project that leverage on the same prefix (and my xfProject would end in a smaller mess... but always a mess !)
Again, in that particular Application, a consultant could create BRules needed only in that context, that shouldn't be exported.
IMHO, even if could be really verbose and annoying to write, the better solution is to detail every single item to export.
Regards
FabioG