Replying to old threads is somewhat frowned upon, but... ah well.
No, laptops pretty much expect to receive certain voltage and amperage from their charger. You cannot really set the input by software.
In theory, IF you downclock the cpu and GPU a lot, they will not use their maximum power and at that point will draw less power. The problem with this approach is that the first part inside laptop, the battery charger, STILL expects to get X watts of power and will pretty much use all that the other components wont use of that to charge the battery.
So.. no, you shouldn't really use chargers rated for less than the original ones.
As I noted above, few bad things can happen from prolonged use.