I too have mixed feelings about a sequel, particularly so soon. I'm a big fan of the first game, and agree with your comments on the chainsaws etc. Perhaps a half-way house where they work for a certain amount of time then stop (assuming they're powered by petrol, and would clog up with overuse), at which point you can lob it at the zombies.
A further adaption of the Survival mode would be/have been good too, where you can lay traps similar to in the original Half Life 2 against the zombies, with shelves or barrels lined up to drop if you shoot what's supporting them, to really make good use of the great physics engine that the game has. Some people had critisized the frying pan addition, but in all fairness, I'd use anything I could get my hands on to increase the distance between myself and The Horde, be it a frying pan, chair, broom handle etc, but they could do it so the heaver the object, the more damage it gives, but the longer the time between swings due to getting tired.