Hriston
Dungeon Master of Middle-earth
A ranger ability that ignores or can remove exhaustion levels would multi-class really well with a tempest barbarian. Not that that's a bad thing.
I was thinking of something like this, based on Indomitable:
ENDURING TRACKER
Beginning at 2nd level, you can reroll a Constitution saving throw versus exhaustion that you fail. If you do so, you must use the new roll, and you can’t use this feature again until you finish a long rest.
You can use this feature twice between long rests starting at 6th level and three times between long rests starting at 18th level.