It's actually an interesting thought since the technology is obviously there. Hell, my '95 camry, if you floored it while the engine was still cold, it would shift at 3500rpm instead of redline until the engine got warm (though it was an automatic).
So would it be hard to program in a throttle limiter of sorts based on engine temp? Why not if it's drive by wire throttle, right? My guess is, such a device is not equipped on Subaru's (and a lot of cars), because it would cost more $$$ to implement it. I can't think of any other logical reason. Maybe there's some safety/liability component?