I know you said you've tried other litters, but have your tried Arm & Hammer? Its great for kitties who don't like the feel of regular litter because its very sandlike, with very fine grains of litter. Thats what the rescue recommends to people who have declaw litterbox issues. Have you tried sand? Maybe mix in some baking soda to help hide the odor.

And the wee-wee pads didn't work? If he's declawed he shouldn't be shredding them. They do a good job of soaking up urine so you don't smell it - Nature's Miracle makes one where they have odor protection in it.

As for the carpet, you wouldn't have to clean it. Just toss it after they use it. I can order you a TON of carpet samples and send them to your house (ahhh, the power of being an interior designer! bwahahahaha). Just toss them every day. You can also pick out remants from the dumpster at the local carpet store. They always have large remnants left over from jobs. Often big pieces you can take out as a roll! Just cut it up as needed.