There are several applications (autodesk apps, Mastercam, masterworks, masterspec, National Instruments, solidworks, etc) today that are absolutely ridiculous to package. Given the annoyance and difficulty at packaging and automating the installation of the above apps, I think it would be well worth allowing custom apps to be shared or exported.
I agree with this however it might be wise to be sure that customer-specific items such as license codes/etc, are omitted (or placeholdered).
I know that one issue would be around sharing the actual files, but an import/export process for the metadata like install/uninstall commands, dependencies, etc.
Being able to share small files such as icons, scripts, ini/answer files would be helpful as well.