Remap copy and paste shortcuts

First, Ctrl+C and Ctrl+V are not system wide shortcut keys. They are defined by the application that you use. It is a very widely used convention to use these keys for copy/paste.

As a consequence, if you want to change these bindings, you will need to change them in any application where you want them to change. The accepted answer in this ask ubuntu post may provide some first ideas.

Alternatively, you could redefine the keys of your keyboard, such that Alt works as the Control key. That way, your copy shortcuts indeed will be moved to Alt, but also any other shortcut that programmers defined to be triggered by Control.