If I was in charge, you'd pay a low rate for the first xx kWh for each person. I live alone, am very careful, and use about 5 kWh per day, so say the first 4kWh is cheap - 16kWh for a family of four.
After that, it would go up to the full rate, whatever that is. That way, the basic cost would be low, and everyone would have a big incentive to save power. People heating houses that are too big for them would have to pay the difference or sell. People who can't be bothered putting on jumpers in winter would pay for the privilege.
And no more of those expensive pay-as-you-go rates - that's just exploiting poor people.
This would be easy to do, even for people without smart meters.
Also, I'd make every company offer a variable source tariff - where you paid a much cheaper rate for renewables when they are available, a fixed rate for nuclear (because it is fixed) and a variable rate for gas / oil /coal. Its not fair that the rate is the same whether its from cheaper wind / solar, or extremely expensive gas.
This would be a bit tricky to programme, but I reckon its not far off what Octopus are doing with their agile tariff.