Honestly, I would not be disappointed if the Nationals took either Harper or Taillon in the upcoming draft. I think both of them are going to have great careers. Obviously there are questions surrounding each of them, but I do not think they are big enough to stop a team from taking them with the top pick. I imagine that both player's agents (Boras vs. Hendricks Brothers) are going to aim higher than Strasburgs 15 mil, hopefully settling for something less than that number.
In a perfect world scenario, the future sounds thrilling with either pick to me ("Strasburg throwing to Harper" or "Strasburg and Taillon pitching back to back").