I don't mean to imply this would be a cakewalk, but my guess would be about %30 time to digitize and edit the footage back together, versus perhaps %70 time to redo every special effect in CGI.
I was just thinking about this and was curious how much it would cost just to create digital intermediates of the dailies. I know all the editing and SFX do-overs would be quite costly but just getting the scanning done in the near future might be prudent as film doesn't last forever. If I were heading a project like this I would get a jump on future technology and do everything in 4K
. The scanning process would be more time consuming and storage intensive but a larger, downsampled source would look better on blu-ray and you would have the source material on hand for future re-release down the road when 4K cinema resolution is common in the home.