Yes, you could even have sappers to disarm mines within the Academy's castle.

If you're fighting against the Academy, use sappers; against Sylvan, use gardeners; against Warlock, use electricians; against Necropolis, use gravediggers (this is in the context of sieges):D :D :D :D

As for me, I would create individual machines for each race (for example: elves - as they don't like machines and all sorts of dark technology (see the race description), they could replace the catapult with an ENT, which would throw stones (like a catapult against the walls), and I don't know what they could create instead of a ballista, etc. By the way, like in Warcraft, you could let Necromancers use a corpse cart as a catapult!