One alternative to the "lightning" exposing the Emperor and fighting with lightsaber, for me would have been at the point in the movie when Mace and Co. go to arrest Palpatine, there whould have been no saber battle, Palpatine casually would have used the force to throw 2 Jedi to their deaths out the window after approaching him, then used lightning on Mace, blocking the lightning with his lightsaber Mace could have backed Palpatine into the corner, Palpatine intentionally stopping before Anakin arrived, Mace then prepares to kill Palpatine, Anakin "saves" a faking Palpatine at the last moment, Palpatine unleashes the full strengh of his lightning on Mace and while using his power his true look slowly reveals itself...

Personally I would have liked if Palpatine would have been more subtle at revealing it at a later point to Anakin after he had already turned to the darkside, while talking to Anakin about the power of the darkside and simply turning around in his chair.

As it stands, one of my kids at first viewing thought maybe the lighting itself scarred Palpatine, instead of it revealing his true identity.