Maybe I can add an interesting morsel here from the man himself. Over at reddit.com/r/bourbon, we sent a Q&A to him earlier this year (I think?) and one of the questions was "Why not rye whiskey?" Here is the answer:

We could add 16% rye grain to our OB mashbill - and reduce the corn by that percentage - and have a straight rye whiskey. As an interesting option we could also use our “K” yeast, which generates spicy flavors. Another option might be a 90% +/- rye mashbill using “O” yeast which generates a rich and full-bodied fruity flavor, or.... Hopefully, we can begin distilling a straight rye before I retire, but even if this were to come to fruition the first barrel may not be dumped for bottling while I’m still master distiller. I believe rye takes longer to fully mature relative to Bourbon. So, if we started production of a straight rye in 2013 you would not see it in a bottle until 2020 or later. We won’t take any short cuts.