SHA256 bitcoin clone that can be done on CPU-GPU

I'm afraid that there are gaps in my knowledge about the encryption and discovery process for bitcoin and its SHA256 clones. Would it be possible to build a SHA256 encrypted currency that is compatible with Bitcoin (similar to the way Namecoin is) that provides something like one coin per hour of mining time, even on a CPU or GPU, rather than merged mining with ASICs. Laptops and graphics cards could therefore be underclocked to save power, threads could run in the background, and older machines could be used for mining.

I guess what I'm suggesting is a Bitcoin clone that uses the same encryption, software, and similar wallets, but varies the reward daily to maintain a stable value. When the price drops, rewards are reduced to the minimum until the number and value of buy orders catches up. Instead of increasing difficulty over time, it would simply pay out in tiny amounts for the number of thread hours running on the SIMD hardware on modern CPU's and GPU's.