I don't see the benefit of just re-mastering some of the episodes -- that might be enough to put on home video, but it wouldn't be enough to widely syndicate. If CBS is going to make the investment of getting a team together to re-scan the negatives and build CGI assets, that's an awfully big investment to make on such a limited prospect as a "Best of" DVD or Blu-Ray.
Exactly! Economics of scale.
I'm excited by the prospect of seeing the original film elements in their full glory! It's going to look utterly fantastic! And as an added bonus, there's bound to be loads of deleted scenes and goofs that we've never seen before. There must be hours and hours of footage that's never been seen anywhere else.
In terms of adding new elements, I would love it if we could see some different shots of the Enterprise, rather than recreating all the same stock shots again. I suppose if they do use CGI for this project, then creating new shots is inevitable. I look forward to it!
Also, I want them replace the Angel One matte paintings with brand new cityscapes. Please!! It's vitally important!