Elderflowers won't add body and their flavour would be lost in red wine. Oak chips don't add body but deepens the flavour. Reducing the proportion of added sugar helps, but more fruit must be added to compensate. Apple juice is an inexpensive 'body builder'. Using it instead of water, say 2 litres per gallon, will also reduce the need for added sugar. The higher the alcohol, the more body, as it is thicker than water. 13% abv is significantly 'thicker' than 11%. Glycerine will also help, at the rate of up to 25 ml per gallon of wine. Another good substitute for adding sugar is minced dried fruit. Currants are particularly useful for red wine as they are in fact dried black grapes. Half a kilo per gallon will provide 350 g of the total sugar required, plus all the other stuff that grapes provide which white sugar lacks.