If we want to produce some more excitement we can copy the idea from the Winter Olympics event where cross country skiing is married with shooting rifles (I don't know what that sport is called).
Like we can have the driver get out of the car and change his own tires. Or even really shoot a rifle for God's sake!
OK, enough joking. The first improvement on KERS I would think of is not in handing different power limits to different people. It is actually the freedom of using the boosts. Instead of limiting boosts per lap, the quota should be for the whole race. Drivers and race teams can then make their bets - will they want to spread the usage out to minimize average lap time, or will they go for more opportunistic strategies to bet on cutting out some really quick laps when the opposition is pitting / something happens on track?
As for your proposal, I would firstly raise the question whether the little bit of difference in KERS power will result in observable improvement in the racing. We've seen in 2009 that everybody tends to use KERS at the same spots and if we are talking about two cars fitted with KERS that differ by only a small percentage of power, I doubt if we can see any effect at all on track. To me, it is more like the cars at the back have progressively more number of boosts per race. This should give a clearer advantage, as well as being easier to administer than setting different KERS power limits.
Secondly I think handing out gifts/penalties based on qualifying result is just not the appropriate thing to do, IMHO. I think they should be given according to the current standings / previous race results. I don't think teams will have that much foresight as to plan scoring less at one point to be in a better position in the future.
Having said all that, I do agree tweaking the boost factor is much easier than attempts like adjustable wings. On a side note it brings me back to the idea of weight penalties for previous race podium finishers / standing leaders. A combination of these might actually produce something good for TV.
Oh, and of course, if your/my plan is to really work, KERS has to be made compulsory, which, if I'm not mistaken, is not the case for 2011.