If you think about it, Academia Island! All the initial equipment they use as Liveman is based around their first encounter with Volt - a shuttle that suddenly lands on-campus, and Kenji/Kemp's use of a laser gun. The Humongous Mecha (themselves meant to be Air, Land, and Sea supremacy vehicles) and Bimotion Buster, then, are overkill. Which is exactly what they'd like to do to Volt.
Given that the mere existence of the Humongous Mecha on an academic campus would have had to have broken a couple of treaties at the very least, and that they could only have been built with tacit (Volt wasn't aware of them, so certainly not public) local support, you have to wonder whether Liveman was created to be a local defense team, or a government-blessed anti-Volt team - either way, an original backstory for a Super Sentai show.
Wasn't it established from the start of Liveman that they were working on SPACE technology, though?Maybe the mecha were meant to be a test-bed for space propulsion tech (definitely, Gran Tortoise would have fit there, along with the Falcon Jet), and were weaponized when Volt's plans were made known around the time Kenji and the traitors left.