If the game was coded competently, I don't think it should be that hard to do this. Problem being it probably wasn't.Well, not every single image. They are layered. The backgrounds needed expanded from 4:3 to 16:9 display ratio. Any special images, too. Some of the layers might have seen some expansion (like now there are full standing nude poses for all(?) the women in the game). That being said, most - if not all - of the layers needed reposing because of the new display ratio.
98% of the art for the tech update is done.
90% of the writing
78% of the posing
57% of the coding
0% of the bugs from all the above are done for the tech update (because they haven't tested it yet).
If it were me, and I were making this game, I would make the art so that we could program in pre-determined entrance and exit points for characters on either the left or right of the screen. During the transition to 16:9, you could change those entrance and exit points in one place and it would solve the vast majority of the posing issues, with maybe a few minor changes.
But maybe there's something I'm missing here that makes it harder, but it can't be hard enough that it would take more than a year once you hire some coders to do this mostly busy work.