In FDesktopPlatformWindows::OpenDirectoryDialog, BIF_SHAREABLE is one of the flags. This is preventing us from being able to choose a network folder to package (on Win7 systems). It looks like BIF_SHAREABLE prevents already shared/mapped network drives from being displayed. Apparently this is a known (and confusing) issue.
I’m using UE 4.6.0. I’ve made this fix locally, but hope this can be changed in future versions of UE - otherwise consider this posted for archival purposes.