instead of using peanut butter, why don't you go one better and add the actual peanuts? You can completely grind them down (like when making homemade peanut butter ) or you can leave them a bit crunchy. I bet that is going to taste a whole lot better than just adding something out of a jar in this case. You can also add a bit of butter (or the spread of your choice ) to make it more buttery, if you are not happy with just the peanuts.
I am British, but I've been living in Germany for the last 20 years or so and they are very big on using the "original " ingredients - meaning " you want the peanut butter taste, use peanuts! or, you want the marzipan taste, use almonds!" And there never used to be anything other than scratch baking done over here, but in the last year or 2, there had been a slight interest in packet mixes, not much, but a little. I know that is a whole different ball game, I was just trying to explain the mentality over here.
Have fun experimenting with flavours and I hope it turns out how you would like it to.