Nope, impossible for many technical reasons. That said, it might be one day possible because people are actively pursuing Android OS on iDevices. So farm no go.
You can, however, run something called Dreamboard. The program is a theme platform requiring Dreamboard Themes. And you can DL themes that make your device look like Android, or Windows, or Ubuntu or like nothing else you've ever seen.
As for jailbreaking iOS devices, yes, you can highly modify iDevices. We Jailbreakers use something called Cydia, a front end to Repositories for things like apps, themes, tweaks, and other stuff. We use Winterboard to theme the device.
One thing I do not think Android users can do is mix and match parts of themes. I can use icons from one theme, wallpaper from another, a lock screen from a third theme, and so forth. I change icon label colors, text, and so forth. When I 'respring' the iDevice is changed. If not satisfied, simply uncheck the options in Winterboard and respring.
You can also create free themes online directly from your device.
iDevices are every bit as easy to customize as Android devices.