I see what you mean, but not really doable for me. It's a 7.5 mile ride one way and I prefer bike specific clothing for the longish ride, and I prefer non-bike clothing during the day. If it were less than 4 miles, I'd probably entertain that idea.

And leaving stuff in panniers is a no-go. I did that for a while and it seemed safe enough, but after a while, I just didn't feel comfortable leaving my nice bike clothes (merino wool and all) sitting on my bike. Even then, they didn't get very dry. The cold didn't help. That and I've recently gone away from panniers.

I guess the mesh bag idea is as good as any. The main thing is to keep the dry clothes against my notebooks, etc. I spend a lot of time sitting (in class, or working on a computer), and sometimes I'll just crack the bag to keep the air flowing, so the mesh bag would be pretty functional at that point.

So far, pretty good input. Keep the ideas comin'.