Maintaining Macro Enabled Templates (XLTM)

I'm new to macro-enabled templates. I have to hit the ground running on this due to circumstances beyond my control (Background detail = I am taking over somebody else's project which is heavily tied to a XLTM.)

I think I am OK with the general concepts of what a XLTM is and when you would want to use one.

What I think I need help on is how to best maintain the XLTM template. Essentially I don't want end users able to edit the XLTM. But as the developer/maintainer I need the option to do so. What is a good approach for this?