Personally, I think your plans are good dms. Lofton will be good for roughly 100 games batting in any of the top 3 spots in the lineup (406 + 40 from the extra 10% = 447; divided by 4.5 PAs/game = 99.3).
I might find a way to get Castillo up in the #2 spot vs ies or if Lofton is fatuged. Even though he doesn't steal many bases, getting him to walk in front of Teixeira and Chavez should lead to more than a few 2 HRs or scoring from 1B on a double.
I would also mention that I would be more concerned with stolen base percentage rather than raw steals. If any of your guys have under a 75% stolen base percentage, you may be running yourself out of RBI opportunities in front of your power hitters.