That’s just it, Jordan and FASA were going for more than “a measurable impact.”Yes, but that's still over the top. You don't need big #s to make a measurable impact.
The Clans were meant to represent an existential threat to the Inner Sphere.
Jordan puts it best in a gameasutra article, “‘Of course, the result was not a resplendent Rime, but a technological and sociological decline into the dark ages, setting up the opportunity for the Mongols to invade,’ Weisman explains. He adds that people who know the history of Rome will see parallels to BattleTech touchstones like the Noble Houses of the Inner Sphere and the Clan Invasion.”
It took Clan Tech to set the stage for the numerically inferior Clans to offer the combined might of the Inner Sphere the manner of existential threat Jordan and FASA were going for. Of course that existential thread was doomed to failure... at least in the 3050-era. : )