if you can sew okay, then yes that will work. cut the two jackets and pants relatively even. then either use a sewing machine, or if you do it by hand, double thread it (fold the thread in half before putting it through the needle). and just sew sew sew. don't worry about it being perfect. it can be sloppy because if two-face, in his insanity, made the suit himself, it wouldn't look so great. i don't think you'll have to worry about that. i think you can do it. and maybe even dye a tie down the middle. that would be cool too. your biggest problem would be the face. there are any number of ways you can do it though. just look up some basic make-up effects online. burns, scars, things like that. i'd suggest buying some make-up (although that gets expensive) so you can test a couple different methods out before halloween comes around.
hope that helps, and i'll be interested to see how it turns out. be sure to post pictures and keep us updated with your progress.
oh, and i like the sig. blundercats. classic.