The way that I have accomplished this in the past is to use a private NuGet server (or a source such as Artifactory). If you want to use a private NuGet server, you could host your own using
GitHub - NuGet/NuGetGallery: NuGet Gallery is a package repository that powers https://www.nuget.org[
^] or, even better,
Baget[
^]. Whichever solution you choose (and there are other private NuGet offerings), you would separate these other classes into their own NuGet entries, which would be built separately by different Jenkins jobs.
Now, when you build, set your Jenkins NuGet repositories to be both nuget.org (for the general purpose NuGet packages) and your local NuGet server to pick up your local files.