IMNSHO - merely lowering down to Legacy height will cause some issues in geometry, screwing up the camber curve. Improves static camber, but go into a corner and you'll end up with less negative, maybe positive camber. I think.
If, OTOH, you remove the spacers that make the difference between a Legacy and Outback, it may be another matter. That's more work.
And last, do you really want junkyard shocks?