No more sandbox against league opponents
This was a feature for the tournament, so I know it's possible, but right now it's kind of dumb. I just won my first league game against an opponent who was 100 ELO above me. I only won because I played about 10 sandbox matches in a row against him until I found a tactic that worked.
I'm fine with sandbox in general, and I'm not against meeting league opponents in random sandbox matches, but being able to play so many matches in a row against a chosen opponent when you are about to face him in the league really favours whoever is has more time.
As an added note, I would love it if you could choose your side in sandbox.