I'm afraid there isn't that I know about, widgets inside of widgets yet... there are widgets that allow you to "compress" icons to smaller space but that's just because they're emulating the icons themselves. That's pretty mundane in itself.
I can only really suggest you to very carefully order your widgets, find smaller ones if possible, and use a launcher like Zeam that lets you have up to seven homescreens, and change the number of icons you can have on each, and the widget size once you put them on. Things get squished, but sometimes it works out great.