A year later, here's what we came up with and have been using.
We now include the following line in the Application_Start()
method:
Database.SetInitializer<EFLib.MyHousing.MyHousingMVCContext>(null);
This causes it not to throw a fit if the current database model doesn't exactly match what's in the code. While there is still potential for problems if non-backward-compatible changes are made, this allows for new functionality to be added without the need to re-deploy every site that uses these libraries when the affecting changes are not relevant to that particular site.