Of course you can target the war machine. The rules are very clear.
Show this to your group- O&G army book, Doom Diver Rules, p. 27: " ...the player is allowed to move the impact position... this many inches in any direction."
In any direction. Not 'towards the original target point', not 'towards the target unit'. You can shift D3 inches in any direction you want, including towards a jucier target.