I'd like to try making a custom template for VS 2015 and VS 2017, using one of our primary, skeleton projects (we call it Core) as the template project solution. That way we can have a template we can use within either VS 2015 or VS 2017 to create new projects based upon our Core project.
However, I'm sure I'm going to get something wrong, at least the first time. So I'd like to know if I can use Core in more than one custom template project?
Yes, you can export your Core as the template in both VS 2015 and VS 2017.
Actually you can freely export template multiple times with different template names from an existing project/solution (Just change the settings accordingly each time based on your requirement).
Then create projects from the customized templates same as the build-in ones. One more thing, you may need to resolve the project dependencies/references manually in different machine or solution.
To export the template:
For creating the custom Solution template please reference this article:
Visual Studio: How to create a solution template with multiple projects
Note:
You need to modify the customized template to remove the source control label if you export the template from a project/solution which has been in source control, otherwise the new created project from the template will be considered already in source control. See details in my another answer :Adding project from custom template to VS does not add it to TFS
