He is their leading scientist. Knightmare production was at a fucking total standstill for decades before he built Lancelot.
The only stuff we've seen Rakshata know about is cybernetics and whatnot, which explains the Guren. Her experimental radiation arm + a design that's very easy for humans to use. The Gekkas, Akatsuki, and Zangetsu are all based off of Guren, just with lower specs and no claw.