The best way to make a really good red wine is to start with really good red wine grapes.
But then you want to make it with a kit or fruit. OK, at least start with a really good red wine kit.
To address you other issues, The best red wine I have ever made from non-grapes, by far, is dewberry or black berry. Made dry they can come out very similar to a light/medium bodied Beaujolais style wine. I like to use
5 to 7 lbs of fruit to a gallon.
You mention adding body. Bananas are a proven way to add body to most wines. They make a nondescript wine so they do not change most wines they are blended into but they will build up body. Just remember that a lot of body is great in a wine you are drinking just to drink wine - patio wines, but it can get in the way of good food if you are having it with a meal.
I was going to mention bananas too but thought maybe not as the post that guy referred too discussed possible problems with things like pH. Since it's out there now - bananas have a lot of potassium so they could influence the pH of the kit significantly, something that's definitely better avoided.
Blueberries! I just bottled 13 gallons of a very good wine made just from blueberries. Nothing added. It is wonderful. It is very healthy also. A red wine made from blueberries.
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