It's no big deal to create a footprint for the Nano in DipTrace, that should be very easy. Yep, I managed to get my JST connectors installed. 
I've created footprints for other parts, and I've thought about the Nano as a possible candidate. When you're building your board with the Nano, consider having it above the board enough to put components under it, that makes for a more compact assembly.
Here's an MP3 module that accepts an RF receiver on the left, and an MP3 module plugs into the headers on the right. My circuit provides power and has a uP that converts the radio data to commands for the MP3 module. By mounting all the components on the top, I was able to make it easy to mount the board using DS foam tape. No reason not to have the stuff under the MP3 module. 
