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.
I read a article a few years ago, sorry can't recall citation, that stated ~70% of the flavour compunds in a wine are from the yeast and formed during fermentation, so my advice would be for flavour choose a different yeast.
The body of a wine comes from a few factors: residual sugar levels, acids, tannins, and your water chemistry.
Strawberries and Peach are both low in tannins, so you may want to add some a couple of cups of strong/stewed black tea to your next brew. The tea will provide the tannins that would usually come from with the skins of the fruits: grapes, apples, pears, plums, sloes, or from againg in oak. You could also try aging the wine is secondary on some home brew oak chips for a couple of weeks. You can also purchase grape tannis, and add these to the must at about 1 teaspoon per 5 litres. Can also add in rasins to the must.
If the fruits you are using are rich in simple sugars then you will likely have very little sugar left at the end. This can lead to very flat feeling wines. You can up the pre ferementation sugar levels to ensure that when the alcohol tolerance for the yeast is reached there will be enough sugar left to give some body. You can do this by using more fruit to water, or adding sugar to the mix.
There is a huge selection of wine yeasts on the market, select one that you know and like or one that is pair with a wine that you think would complemented by peaches and strawberries. Maybe a yeast like WyYeast: 4242 might help out with the falvour profile.
If your water is low in Cholride ions, this can lessen the mouthfeel. Adding a tiny amount of common table salt to yhe wine post fermentation can sometimes radically alter the feel and flavour perception. We are talking tiny additions like 1g/5litres.
I like a blend of acids, malic, citric, lactic which I use to get the pH of the must to ~3.2. The acidty can greatly affect your perception of the other elements and also affect fermentation. Sorting out the pH can have a huge impact of your perception of the wine.
Recipe For Strawberry wine from C.J.J. Berry - First Steps in Winemaking p175
2Kg - Strawberries 1.5kg - Sugar 1 teaspoon - Citric acid 1 teaspoon - Grape tannins made up to 4.5 litres of must yeast + nutrient