Shards - you're already practically rating cards on their power level, do the same with shards and have them unlimited
Auction vs draft: I think draft was better and way more exciting from outside perspective
Roles: Reassignable imho, but I don't think if you didn't originally pick one of the roles that you should be able to swap out
Market: I think it's cool but I also think it's rather confusing, so personally Id rather play without it
Sideboard: Yes please
Upgrades: "One of the thoughts we had about this was either have a role where one card can permanently upgrade a card or similar" I prefer this option, I think it would diversify the event more, and for the better
Soft bans: Opinion on that latter, when it comes out