Ellie, What you are asking is similar to exchanging your car's engine for a larger and more powerful one, and, oh yeah, while we're in there go ahead and swap the standard transmission for an automatic. Yes, it can be done, but the parts and labor would probably cost more than what your car cost in the first place. It's the same concept for swapping the integrated electric dryer components in your unitized system to convert it into a gas-powered system. But unlike with your car, I'm not sure whether such major surgery on a washer/dryer unit is even possible -- or legal.
If you honestly prefer the gas-dryer version of this integrated washer/dryer unified system, you would be better off buying a brand new gas version of the entire integrated system, and then selling the electric version on CraigsList, eBay, or whatever. Just be aware that your integrated W/D weighs 241 pounds without a drop of water in it.