The problem with you scheme is that you'd need to create the 3:2 pulldown out of the J3H for the 1200A to record the HD-SDI signal (it can't handle the Cine Alta style 24 Psf) and that will not have "A" frames for FCP to pull out the individual frames to create a 24p project. That's not to say you can't make a 29.97 project, but you won't be able to conform it to your origional HDCAM footage in online.
Perhaps a Kona card could convert the 24 PsF coming in HD-SDI to DVCPRO100 codec; you'd have to contact them directly to inquire. They are generally very helpful on the phone. Contact the manufacturer "AJA".