One QoL i really think would make a difference is swapping out that team up icon (that shows which team up a certain hero is using in the hero selection tree) with a pet icon instead.
I assume there used to be a plan to have team ups work like pets and you could move them from one hero to another, but since i can have 1 team up on every single hero at the same time and swapping them out is easy while (at least for me) losing specific pets and sifting trough almost 50 heroes to find it can sometimes be quite a chore.
So in the end, the team up icon does not really provide anything worth wile, but a pet icon would in my opinion do wonders. :)