I wonder if part of the deal to bring Morrowind into the Empire might have been Vivec helping Tiber Septim attain apotheosis. Comments?

Yeah, the Numidium was the deal, and it fits Vivec's primary role, as divine instructor, to do so.

Big deal. Vivec has been kissed more often that Tholer Saryoni's ring.

Highly doubt it, if you're talking about Tiber planning to become Talos. All we can prove is that Tiber wanted to unite the Empire using Numidium. Him becoming Talos is serendipitous happenstance.