Seems like a neat thing to do every once in a while, and I'd give up flash over smite.
But at the same time, I can't think of a reason to not take exhaust on any support. The ability to weaken any fed enemy and single them out seems like a waste by comparison, especially considering you probably shouldn't have the gold for Cinderhulk for a while. You already need to buy SS, but then having to purchase the jungler item and upgrading it before you get any use out of your smite seems like a huge risk.
If it works for you, go for it, but I wouldn't go and recommend you doing it outside of a group of friends/premade team because it's not considered meta, if you lose you'll be the target, and people may not understand what you're doing. If your team doesn't understand what you're doing, they are less likely going to be able to play around you well, and they won't understand the best way to work with you.