How to add activities to a workflow definition at runtime?

Question

I need to add a couple of activities (Persist is one of them) at runtime to any executing workflow.

The way was done until now was to encapsulate the loaded workflow (which is actually a DynamicActivity it seems) and with a Sequence like this:

private Activity WrapRootActivity(Activity activity)
{
    var sequence = new Sequence
    {
        Activities =
        {
            new Persist(),
            activity
        }
    };

    return sequence;
}

One problem with this I discovered is that you can no longer get the out arguments from this workflow since the root activity is now a Sequence. And the more I think about it I find it strange to use something else as root activity.

The solution I came up with is to use this helper method I wrote:

public static void InsertStartingActivities(this DynamicActivity original, params Activity[] startingActivities)
{
    var sequence = new Sequence();
    foreach(var startingActivity in startingActivities)
    {
        sequence.Activities.Add(startingActivity);
    }
    sequence.Activities.Add(original.Implementation());

    original.Implementation = () => sequence;
}

What do you think, it makes sense? One problem I found is that you can not resume any in progress workflow instances but we are going into production only in a few days :)