It would be cool to have a training Golem (like the one in special training forces area) that we can summon on any location in open world (instances excluded).
How it would work:
It would be used by you/your party members or in case it could be used by everyone - set its HP to unlimited so it does not die within seconds.
Bashing something while waiting for some events/metas to spawn would be cool and it could potentially help people who want to practice some rotations but are too lazy to go to Aerodrome.
This could be a gemstore addition or bought with raiding currency similar to Xera portal maybe?