For posterity’s sake… here’s what a local Subie shop told me, and another Subie shop confirmed the same: “While the chassis' are similar from 06 and 07, the CANBUS system is almost entirely different, meaning swapping of equipment from 06 to 07, is nearly impossible to do correctly. Putting an 07 into your 06, along with SI drive would require changing the vehicle harness as well.”
So, going with an 06 Subaru reman 5EAT (and am told this is the last unit currently in stock in the country).