2011 Forester 2.5X Premium
About the transmission, I can only hope that the TCM is fine. I'll have a chat with my shop if they allow for salvaged parts instead of their own. The first issue that has to be solved that they ran into in diagnostics was that the sensor that detects whether the transmission and the engine are at the same speed was out by a bit (about 15%). If it comes to replacing the TCM I will definitely look into digging for a salvage part because I sure as hell don't want to waste $1100 on it.I know what you mean about the engine, it can sound rough at startup. I only recently learned that mine has a PZEV engine, and that they are programmed to rev at 1500+ when cold to get to temp faster. Its also programmed to idle as low as possible. I have been thinking mine idles too low, but it seems to be the nature of the beast. Cleaning the throttle body with some throttle body cleaner spray was beneficial. Idle is more stable, and the slight hesitation in acceleration is gone.
Changing the serpentine belt isn't so bad and unlike a lot of vehicles its right in front rather than hidden.
With regards to the transmission, I am wondering if the fact that its an older design, means that the same one was used in earlier Foresters and possibly other Subaru models and that it might give you the opportunity to find the pricey parts used. It's rare to have an issue with the transmission control module. You might be able to find one at a pick and pull yard, but you will need to research compatibility.