I've now added one more vehicle to each faction (4 units in total):
Hakurei: Evil Eye - Cheap, fast-moving flyers that can irritate enemy players just by flocking into their base; Very weak in power and armor.
Scarlet Devil: Devil's Breath - A cannon found deep within the Mansion's vault that deals serious damage to large targets and poorly armored units;
Tad slow and takes a long time to deploy, undeploy, and reload the cannon. It also gives off a noxious garlic odor after firing.
Lunarians: Antares - Anti-air vehicle that are excellent against aircraft and can sense cloaked objects at a great range; Lacks ground weapons.
Kappas: Helping Hand - Repairs vehicles in a pinch; Lacks any weapon to defend itself.