IPartialDecorator.cs

public interface IPartialDecorator<T>
	where T : class
{
	T Enrich(T target);
}

PartialAction.cs

public class PartialAction<T>
	where T : class
{
	private readonly IContainer _container;
	
	public PartialAction(IContainer container)
	{
		_container = container;
	}
	
	public T Execute(T target)
	{
		_container
			.GetAllInstances<IPartialDecorator<T>>()
			.Each(d =>
				{
					// allow classes to hook in and build up model properties
					target = d.Enrich(target);
				});
				
		return target;
	}
}

PartialActionSource.cs

// hook this up with an Actions.FindWith<PartialActionSource>() in your FubuRegistry
public class PartialActionSource : IActionSource
{
	public IEnumerable<ActionCall> FindActions(TypePool types)
	{
		return types
				.TypesMatching(t => t.HasAttribute<PartialModelAttribute>() && !t.GetGenericArguments().Any())
				.Select(m =>
				{
					var actionType = typeof(PartialAction<>).MakeGenericType(m);
					return new ActionCall(actionType, actionType.GetExecuteMethod()); // just grabs the method named "Execute"
				});
	}
}