I've asked this question before and tried the only suggestion I received. My last batch of strawberry/peach was only marginally better by freezing the fruit prior to brewing. I do better using concentrate, but I don't know how to improve the body when brewing with concentrates. Grrrr, what am I missing
In terms of body, you need a balance of acids, tannins, and sugars. If these three are balanced correctly, your wine will have better body. As for flavor, freezing the fruit is a good way to go, but I suggest lowering your water content to get more of the fruit in there, which will inevitably give you a stronger flavor. An increase in the sugar may also help find the flavors that you think the wine is lacking.