I did forget the wheels and the carriage and the details.
Anyway, it's definitely not useless in forests unless you're looking at a jungle sort of forest. Ballistae are very useful whether you're assaulting fortifications or fighting out in the field. It turns armor into a nonissue and allows us to take down individuals, their equivalents to our Chanters, perhaps, or knight-type soldiery, without needing to batter them down first.
Oh hey, can't believe I forgot to consider this:
Temple of the VoiceguardFar away from the eyes of others and the spies of the enemy, located on the rocks above and around a sacred pool of water and mana, we have constructed a mighty fortress, a great keep and tall towers all looking down upon the sacred grotto. Inside the sturdy keep, craftsmen create Runes of Windforged steel to hold the mana of the sacred site, while higher still above the desolate crags dwells the Voiceguard. Here in reverence they practice their arts, growing ever stronger, ever more capable...ever more plentiful. Pulled primarily from the most devout of the clergy, those who wish to be Chanters are trained here, to join the Voiceguard and be sent to war...albeit in a supporting role for now. Their divine Wind cools our soldiers on the march, Smoke conceals them on the field, Poison coats their blades and bolts, Embers start fires great or small.
If this is an actually doable design according to the GM, then the Temple will be my vote. If anyone else wants me to I'll still fix the ballista writeup because it's kind of insufficient for sure.
Gathering of Lye "Leather Production" (1) TricMagic
Skyarms (1) Doomblade
Bluesteel Bō (1) TricMagic
Temple of the Voiceguard: (1) Madman
White-blue design (2) TricMagic, Madman