Babka dough is very close to challah, and Leah seems to have mastered them both! I don't think too many people would complain if you used my go-to challah dough instead of Leah's yeasted sweet dough. You can't lose either way.
I was convinced that in a head-to-head battle, chocolate would win over cinnamon every time. (Debbie, my wife, strongly disagreed.) Then I put my theory to the test by making both of Leah's excellent fillings one day, and was I ever surprised. As much as I loved the chocolate, the cinnamon walnut won the throw down convincingly. I am a cinnamon convert!
That said, no reason to deny chocolate babka to yourself or others. And, as good as Leah's chocolate filling is, if you have a jar of Nutella handy, it's a convenient and surprisingly decent substitute!