For me, unpolished toenails are much more aesthetically pleasing. When I see polished toenails, especially if it is opaque polish, all I can think about is that the polish may be hiding fungal nail infections, which seems to me very gross. I almost never polish my toenails, and I walk around with my lovely healthy toenails fully exposed to the sunlight (and possibly shocked toenail polishers!), and as a result I have never ever had the dreaded yellow nail fungal issue I have seen in toenails kept better covered than mine.
If I were to have the dreaded yellow nail fungus issue, that would be all the more reason to expose my toenails to the sunlight, though perhaps only in the privacy of my own back garden! I think for some people it is a bit of a vicious circle: they paint their nails or wear closed-toe shoes to cover the nail fungus, which makes it worse. So I think your idea of letting your toenails breathe is actually a very good idea.
Sorry to be gross!
Sarah