I've known guys who have done both- gone from fixed wing in one service to RW and FW in the Guard. They have a short RW transition course for FW pilots, though normally for hard headed Air Force types such as MikeD. Needs of the service, so you may find a unit willing to take you.
Also, be aware that you may have to go back as a WO1. When I reverted I became a CW2, but then they changed it to WO1, though I think you make CW2 after a year.
Back in Viet Nam that was the case. Not sure when they did away with initial FW, but I think it was in the '70s.
Everyone, even the MI types, initially have been going to RW training, then a FW course.
The award of the contract to CAE may mean the Army is considering a change to this, but I would not count on it happening overnight.
Not sure what your goals are but going to RW flight school may not be all that bad.