Ballard passing on Senate this year is somewhat strange but less so passing on Governor. If Indiana is going to have a second Republican Senator, as is likely, I'd prefer him.
Stutzman running presents a small opportunity for Mourdock 2.0, but he's far more likely to actually make it into office. So...
Messer is unlikely to run for higher office, as he, like Pence before him, is seeking House leadership. If he gets denied, perhaps he, like Pence before him, will seek higher office.
What's nice about Ballard is he's a rare GOP big city mayor, who would understand urban issues in a way most GOP Senators do not
The one thing that could be used against him is that homicides skyrocketed during his tenure as mayor. Last year was his final year in office, and it concluded with a number of homicides not seen in over a decade.
Then again, maybe it won't be a liability. *shrug*
It would be interesting to see another Mayor of Indianapolis claim this seat. This was Richard Lugar's seat. Lugar was also a Republican Mayor of Indianapolis.