Drop bars are going to be your friend on a long commute like that. The additional hand positions and ability to get in the drops to thwart the wind can be very valuable. That said A CX / gravel grinder bike is my recommendation. In my collection I have 2 CX bikes that I use for commuting, round town, long gravel rides, road rides, and cross country style single track, the ability to run varying tire widths and the geometry means the can truly do almost anything. I have several another purpose bikes (road, mountain, fat etc. ) but the CX bikes get the vast majority of the miles.