I'm still a little confused about the part where you consider yourself a Conscientious Objector but still want to join the military. The relevant MILPERSMAN aritcle defines a C.O. as "their religious training and belief have a firm, fixed, and sincere objection of their participation in war in any form, or the bearing of arms." If that's you...why are you even talking about joining the military? That's what we do, guy - bear arms and hurt people when the President deems it necessary. It's like asking if you can be a firefighter without actually having to fight fires.
Anyway, this has all been entertaining, but I think we've answered your question. You cannot join the military as a regular line officer and stipulate that you be restricted to non-combatant duties.