Hey, from the details I understand that you have ready themes (templates) that you want to add Tumblr theme(s) operators to it, right? otherwise
"Someone familiar with Tumblr can do this in 1-2 hours." that's impossible, because creating a template itself takes approximately 4-5 days to build, anyways if the point of project is turning HTML templates to a Tumblr theme it could take 1 day by the way can you elaborate on the option of bit more?