What would be fun and interesting to have are dummies that simulate monster actions from high level trials. Let's say for example, you get in to an "instance" or an open area where the dummies would be situated and have them cast you at random times AOE attacks like, let's say plumes and you would get used to the dodging mechanics.

Then again, for that we're supposed to be using Guildhest, to teach us gaming mechanics. But since guildhests are time limited and dummies would be there for as long as you need them I see a benefit of using that over guildhests.