Seems like a replacement complete longblock might be more cost effective approach time/labor wise. A lot of labor involved in swapping heads & such, also "old wine in new botles" comes to mind. I'm not familiar with Subie's policies, but when I owned a Sonata Sport Turbo with the problematic Theta II engine, that was their approach as they replaced thousands of complete engines under a federal recall. I never had an issue with the car, and my GF has it now, still running strong and has a lifetime unlimited warranty on the basic longblock.
I bet the techs at the Subie shops are getting real proficient at swapping trannies.