Updating .NET Standard libraries without republishing the consuming site

I'm starting work on an ASP.NET MVC Core site. It is a parent site that contains subsites. Each subsite is its own .NET Standard library that uses embedded views. My boss would like us to be able to update these subsites by copying the .NET Standard libraries to the server without using NuGet and without republishing the parent site. He thinks we could use reflection to do this.

At first I thought this was a fine idea, but, given the way NuGet automatically handles bringing in any dependencies, it seems that doing it this way would take more time and effort than you'd save. I suppose my question is this: can you folks think of a fairly efficient way to update .NET Standard libraries, including all dependencies, that wouldn't involve updating NuGet packages and republishing the site?