Can you voluntarily exhaust a unit (like Pitt Rookie) without performing a standard move or other game action that causes exhaustion?

Ruling: No, you cannot voluntarily exhaust a unit without performing a game action. Exhausting is a limited action that can only be done when an effect or discretionary game action (like a standard move) instructs you to.

Sequence:

• To exhaust Pitt Rookie at Battlefield 1, you must perform a standard move (such as moving back to base)
• The exhaustion occurs as part of that standard move
• Once exhausted, Arena Bar can then buff the unit