A) That is not a good translation of the Hebrew. This is better. מֵעֵת הֱיוֹתָהּ, שָׁם אָנִי; וְעַתָּה, אֲדֹנָי יְהוִה שְׁלָחַנִי--וְרוּחוֹ. {פ}
That is the way it is written in the Hebrew. The last word is ruach- spirit, and second to the last word is shalach-to send me...put it together you have:
16....and now, the Lord God has sent me, and His spirit. טז. 17. So said the Lord, your Redeemer, the Holy One of Israel, "I am the Lord your God, Who teaches you for your profit, Who leads you by the way you should go.
IN CONTEXT, the person speaking changes, this is something that Isaiah does on several occasions. And remember, in the original Isaiah, there are no verses and chapters, so it makes more contextual sense when you incluse verse 17. So, verse 16 is Isaiah speaking of himself...The LORD G-d has sent me (Isaiah) and his spirit (of prophecy).
B) Your rendering is also poor hermeneutics. A person must use passages in the light ie clear, to shed understanding on those that may not be so clear. At least a dozen times in Isaiah alone, G-d say he is alone, no other, no other savior. So, then why try to use a passage like 48:16 and twist the content to shoe-horn a meaning not there and create doctrine? If you simply take him at his word as you claim, you would rest upon the dozens of clear passsages where G-d says he is a perfect, solitary unity. ANY other attempt to create doctrine of a composite god stands against G-d.
Another interesting note... I'm not a fan of KJV because of its obvious translation errors. I tend to use it posting here because of other FReepers reverence for it. I do that to keep the discussion theological rather than translational. I used it in my post to you out of habit. Sorry about that. The Catholic translations (i.e. Douay-Rheims) translated the passages correctly. Here is the excerpt:
16 Come ye near unto me, and hear this: I have not spoken in secret from the beginning: from the time before it was done, I was there, and now the Lord God hath sent me, and his spirit.
This is reflected in the New Testament:
John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God. 2 The same was in the beginning with God. 3 All things were made by him: and without him was made nothing that was made. 4 In him was life, and the life was the light of men. 5 And the light shineth in darkness, and the darkness did not comprehend it.
Yes, throughout Isaiah and other places God says we have no other savior. Yet, this passage makes it clear that there is more to the story. God swore by Himself that He would save His people, Israel. Such an oath has blessings for fulfillment and curse for not. In swearing this oath, He knew that He would die on the Cross to redeem mankind in a way that man could not do for himself. He accepted the curse of the oath on our behalf and became the sacrificial offering of the New Covenant.
By the way, the Hebraic writing was cool.