I'm definitely not the most informed person to say this but reading the wiki, investigating the files and with all the info the "insiders" is giving us I'm 99% certain that is doable. Civ 5 came with such a modding platform that I wouldn't imagine, very powerful.
My doubts lay on if it would be possible to create completely new functional UI components (i.e. a quick actions hotkeys bar - just an example, I don't want this), because to modify things that are there I don't think it'll be a problem.