**That Jesus is God is fully established in scripture, so if Jesus is God and also a separate person, then what option is there other than the Trinity?**
Jesus Christ is the image of the invisible God, not God the image. Jesus Christ and the apostles/writers of the NT NEVER used the phrase, “God the Son”.
The Father is not an image, but a Spirit (Jn 4:23,24).
In Jn 12:44-50, Jesus does a wonderful job of explaining things. Also 14:11.
Christ is indeed the image of God, but in Him rests the fullness of the "Godhead bodily." He is not a mask. He is not a picture. He is not a reflection. He is the image of God, and is thus a part of God Himself. But not merely a part either, but fully God, and second person in the Trinity.