There's no point in searching out for the obi-wan kinobi of 5EAT mastery, plenty of tuners out there (both on and off this forum) can tune an automatic Legacy GT. I was tuned on a load-chassis dyno with the VDC disabled, it's perfect now
I wasn't concerned so much with the shift speed since the pedal mostly gets mashed for 3rd gear pulls. On that note, will suggest that any overtaking or hard acceleration maneuvers should be done in manual mode. If you want to get the auto mode tuned to your liking, it might soak up a lot of money by the time you're complete with no guarantee that it will be worth it, just a thought.
Some things you can do...
Motyl gear 75-90 (Motul) for front and rear differentials.
Amsoil synthetic ATF for the gearbox. Or Motul ; )
Whiteline rear diff insert PN# KDT 927