This is certainly doable. But you will have to make the fudge yourself, so you can adjust it to be softer, and maybe even fluffy.
Otherwise, the layer would have to be rather thin, so the point where you could just replace it with some caramel sauce or something and get a better result.
Maybe if you heat the commercial fudge, and mix in something to thin it… I can’t guarantee that it will stay solid though. Also it might brown and stop tasting like you want it.
Anyway, to meta this: It’s basically pure sugar and oil. One of the cheapest, most low-quality things one can use. Why not pick something of higher quality instead and make a great cake? (I find Americans limit themselves to very very few types of ingredients and techniques when making cakes. They’re all nearly the same cake and just look different. Which is why cakes in the US usually are very boring.)