> - User agent

This could be fixed with a bit of courage. Firefox could use "Firefox", Safari "Safari," etc. UA sniffing and UA strings are completely absurd at this point, and need to go away.

> - List of Plugins

JavaScript should not see this, especially not their versions.

The last three are harder to avoid for "responsive" web design. One attribute you didn't mention was the font list. There is no good reason for JavaScript to be able to see this. The model should be that the page requests a font, and the browser uses either that or its best try at a substitute.