Here’s one proposal to the book, taken from this webpage.

Structure Romans

If this proposal is correct, it ought to focus more of our attention on chapters 9-11 and the great plan of God who, in his justice and mercy, brought the church into existence as the melding of Israel and the Gentiles. It also means that Romans says much more about ecclesiology (the church) than a cursory glance might indicate.

What do you think?