Kishi did in-fact take models from filler sagas. Not only Raiga, but he also took character models from the 3rd Shippuden movie. All the villain's sacrifices that he used to perfect his jutsu were models used by Kishi in the war. The scorch user, the explosion user and the chubby sensor type; all their models came from the Anime 3rd shipuden movie and were canonized. However in Raiga's case, as stated above, his name wasn't actually confirmed, its just assumed and the 3 sacrifices were never named in the 3rd movie so we can't confirm them either.
Despite all that, we cannot take filler as fact unless its canonized later. Those were special cases and had nothing to do with the true story, just side characters that honestly have no real role.