Well, Detwiler could be used as a swing man, with frequent spot starts. I would not mind seeing Davey give starters an extra day every 3d start, so when we play > than 10 games in a row, start slotting in a spot starter. Detwiler has the most versatile arm (Stras too, but not this season), so it is logical you would use him this way if you did go to a 5+ rotation.
Sharp - ordinarily, a 6th starter costs several of your best starters innings, so it is unwise to use one. However, here we are talking about a staff with an innings-limited ace, and two must-start pitchers in Wang and Jackson who are not clearly better than the 6th starter and likely are worse. If you assume Wang and Jackson are must-start guys, then plopping in a lot of spot starts from Detwiler really only takes innings away from Gio and JZ, and also takes as many innnings away from guys you don't necessarily think are worse than Det (CNW and E-Jax). Keeping Det going multi innings sets you up for the end of the year, too. finally, when det isn't due for a spot start for 4 or 5 days, you can use him and Stammen (or Gorz) as a multi-inning finisher of games (e.g., picking up in the 6th or 7th from Wang or the others), which saves wear on your short guys in the bullpen.