I am not trying to be snobbish or anything by wanting it to be my wine. Since I am a beginner, I want to see what flavors I can achieve instead of relying on somebody's wine who knows what they are doing. Hope that makes sense.
Just for another perspective, when I started my first 2 kits I didn't verify my primary fermenter volumes. I ended up 4-5 bottles short in each carboy. I was not pleased. In fact, I was angry about it. I wanted to follow the directions to the letter and make the wine just as the manufacturer had intended it. I had screwed it up and I wasn't going to know if I had made something as it was intended, or if it was as good as it was supposed to be.
I kept them in vacuum while I thought about how to fix it. I ended up topping them up with store bought wine and they are both great wines.
The other day I took two kits that are still in secondary, one with very prominent acidity, the other a little light for my preferences. I sampled each and a blend of them together. I found them both to be best on their own, but my intent was to blend the two together to make one wine in between the two acid levels.
My point is that you are the winemaker. If you CHOOSE to add wine or juice to your wine, it is still your wine and it is still as good as you can make it. Topping up my Shiraz with a store bought Shiraz didn't make it taste like the wine I bought. I gave it extra time to age and it actually came out better than the wine I bought to top it up with.
There are many variables that will effect how your final wine turns out. Original recipe, what you add after fermenting (juice, back sweetening, etc.), the time you let it age, and so on. The thing is, you control all the variables all the way along. People intentionally blend all the time. Adding another wine is not a failure, cheat, or a lessening of the final product. It may just be part of the process you choose in making your wine.
As we make wines and have more on hand we have more choice as to what to blend or top up with. That will allow you to use your own wines to top up in the future and keep them 'pure', but if you choose to top up or blend with a store bought wine, you still get full credit as the winemaker!