Although I've never tried scones, your recipe makes me want one!
I LOVE to cook and am constantly making recipes more healthy!
1. I would try it with a diet lemonade but make sure it is sweetened with splenda, not nutrasweet. Nutrasweet is NOT for cooking. I've read that nutrasweet become very unhealthy when it is exposed to heat.
2. I would try a low-fat cream in place of full fat. You could maybe do 1/2 low-fat and half regular if the low-fat is not as tasty.
3. Self-raising flour is all-purpose flour plus 1½ teaspoon baking powder and ½ teaspoon of salt per cup of flour. What I've done to reduce the sodium is to make my own with regular flour, baking powder and salt substitute.
I've also substituted some whole wheat flour (for the regular) and it came out pretty good. I'm not sure if this would work for your recipe. I would probably make the other adjustments (lemonade and cream) first then try to tweak the flour.
4. If you want the ginger flavor and feel creative, you could always add a tsp of ginger to the recipe.