BD needs 3 pacers no matter what, Mash, Nazmul could have a bad day any given day, Abul is too inexperienced to be in a FINAL game - hence Shahadat stays.
NAzimuddin having tough time but his out against Lankans was a very good inswing ball, any top oreder will have trouble with that ball. The ball that Nazmul got Mahela is an example, besides his strike rate is good and offer us a right - left batting conbination - Hence Nazim stays.
Law must have to do extra work with Jaharul, Nazim and Shahadat, its one and only final, extra experiment or extra geniusescu move at this point will do only harm then benefit. Stick with team now playing like a gel and rather work on every little weakness in the team.