Spring/fall weekend-casual jacket

I'm looking for a casual non-tailored jacket for the spring and fall. This would be something I'd wear with the temperature in the 50s or 60s, and if the mercury climbed high enough, I'd want to feel comfortable about tossing the jacket into a corner or even (depending on the material) tying it around my waist. Also, a little water repellance would be a good thing, but waterproof probably would not be.

I've considered Harringtons, among other styles, but I'm tall, so I'm self-conscious in jackets that are really short like that.

From what I've read, ventile sounds like a great fabric for this purpose, but it's not widely available in anything other than highly functional garments, and even then, it's pretty uncommon. Not sure why.