Is Super Tengen Toppa Gurren Lagann actually Kamina?
I don't think there is any official source on this, but I would guess STTGL was made with image of Kamina in mind. Kamina was spiritual leader of Dai Gurren Dan and he was most influential person on all main characters, including Simon, Yoko, Viral and other. As that, they all see him as representation of power, freedom and determination. Fitting image for STTGL.

Also note, that at end of TTGL, it is said resurrection of dead people is (at least) morally wrong. So resurrecting Kamina, albeit temporarily, would go against believes of main characters.