Wow,
Not only is this a great idea, I think it is a very original concept to go with SHIII.......
The only thing that worries me is that you will have loooooong loading times when switching between the BdU screens and the actual SHIII encounters; this takes only a couple of seconds in the Total War series, but will take more like minutes with SHIII! I hope you can figure out a way to beat that.....
And last but not least: I do hope you don't get into any legal issues with Ubisoft though....
Anyway, I'm very much looking forward to it!