inside the validators used by Windchill to decide whether a Windchill user will see the Save-As option or not, a check is made to make sure that the user has creation rights for the specific object type in the context of the object to perform a Save-As on.
In theory and in practice, it should be enough for the user to have read+ (if applicable) download rights on a package to see the Save-As button, as the creation rights in the target context (which can be the same as the source context) are checked upon clicking on "OK" to effectively perform the Save-As. Therefore a property or a preference would be very useful, the implementation effort would be very small. If the Windchill idea: https://community.ptc.com/t5/Windchill-Ideas/Ability-to-manage-and-use-saved-config-spec-filters-for... would be implemented, we would not need this improvement and could drop our customization that we have in place now.
This has been tested/verified for Packages: we are using a package in a library as a template (for not entering our specific config spec at every package creation) and we don't want to grant everyone create rights in that library.