What difference you think KERS would have on the look of car? Bodywork regulation have no connection to KERS. There can be differences on engine cover, but all in all, some teams run KERS equipped cars and I haven't heard anyone saying that it had some profound effect on car appearance (well, BMW had boxy sidepods but that's all).
I can't claim to know exactly what difference is, but McLaren and Toyota surely do think there is a difference. The rumours about McLaren building 2 monocoques for the 2009 season must have some truth in them.
Let me give you the direct quote from Toyota's John Howett (
http://www.autosport.com/news/report.php/id/71896):
We will run a car in January with KERS in a monocoque not designed for it, which we could not race, but it will be a test platform - and our gut feeling is that the earliest (it will race) will be mid season. We don't know yet. We are still testing on rigs.
Fundamentally we will have a car that will run KERS, but it will be very difficult to race. That is all I am prepared to say, and we would have to modify it to be able to race."
So what exactly does Howett mean in this case? Reading this, it's logical to assume that Toyota specifically designed a monocoque without KERS, and possibly will modify that monocoque, or will have a 2nd design to be able to accomodate and race with the KERS system.
Ogami musashi, every inch of bodywork is not strictly regulated under 2009 rules. Yes, the cars will look similar from many angles, but not from all angles. The rules will force most of the innovation from the teams to be focused on the front and rear wings, as well as the engine cover. I also expect to see some sort of innovation with the suspension designs.