A place to try out new releases other than a single node in pve would be excellent. Give us access to the three latest character at max, ability to respec them, and a couple nodes to use. Perhaps a 1v1 node and more traditional one. Random encounters for each battle. Something similar used to exist on the Season tab.
No rewards, this would only be abused somehow. Let us get a taste of what may or may not be in our possession 7 months down the road.