In my experience rehabilitative transfers are rarely used. It is possible. You can request a rehabilitative transfer through your unit chain of command after the punishment phase of the Article 15 is complete and actually during the punishment phase. The battalion commander/CSM would most likely be the individuals that would make this happen if the Article 15 was a company grade. If it was a field grade Article 15 the decision would most likely be made by the BDE CDR/CSM.
If this is what you want it would probably be best to prepare a well written one page document that is professional and factual. Leave out the emotion. Explain why you believe the rehabilitative transfer would be in your best interest and in the best interest of the Army.