For instance, my google+ has gone from like 16 megs to well over 200+. Is there a way to flush its saved data once in awhile? Or do I need to delete and reinstall the app to get back down in size?
Of course it fits in iOS. Under Settings -> General -> Usage there's already a listing of apps and how much storage they're using. Tapping on each app is supposed to provide further info, but it's pretty sparse. There's already a button there to delete the app, so it would definitely make sense to also have a "remove documents and data" option as well on this same screen.
iOS 5 beta did indeed have the clear cache option, it seemed un-Appley but I thought they hid it deep enough in the settings so it wouldn't be a problem... sadly it got removed.