Sharp - I'll agree it is not clear that Det is better than Jackson. I'm not sure he's better than Det, either, so I'll say that is a wash. What I would say is that Det is better than Maya and Lannan and Gorzellany, and that it is probable that Wang is better than those guys, too (if he isn't, I agree, jettison him). The inferior innings you would be limiting would be via the 5+ route, rather than the strict 5 man rotation.
Sheehan assumes a 7 man bullpen with a 6 man rotation, with the standard closer, set-up, lefty and righty high leverage middle guys, second lefty, low leverage righty, and long guy or ROOGY. What I'm suggesting is that Davey likes having a lefty and a righty who go multi-innings, and I think in Stammen and Detwiler we could do that. These guys can pick up opposite-handed starters and finish games against lineups that are overloaded with same-handed hitters. this rests short guys and can let you keep a 12 man staff.
The way I'd set up the staff would be - Stras. Gio, JZ, E-Jax, and CMW in the rotation, Det and Stammen as long guys/ spot starters, Storen, H-Rod, Clip, Burnett, and Lidge when healthy, with Mattheus the first fill in for injuries and Gorz the second. 12 man staff.