http://stackoverflow.com/questions/6173566/run-time-registration-with-autofac

Yes you can, using the Update method on ContainerBuilder:

var newBuilder = new ContainerBuilder();
newBuilder.Register...;

newBuilder.Update(existingContainer);

Autofac: cannot resolve dependency using factory after ContainerBuilder.Update()

http://stackoverflow.com/questions/33372771/autofac-cannot-resolve-dependency-using-factory-after-containerbuilder-update

Is it possible to remove an existing registration from Autofac container builder?

http://stackoverflow.com/questions/5091101/is-it-possible-to-remove-an-existing-registration-from-autofac-container-builder