Defeats the purpose of the shell. The shell is for CLI interaction.
command line shell vs graphical shell. My first experience with a graphical shell was dosshell[1]. For a while we called the Windows 3.1 interface "the shell". I guess the terminology has changed since that time.
No. A shell is any user interface. Windows shell is explorer.exe and it used to be possible to change that via a config line in a system INI file.
SSH protocol also isn’t just for CLI work. It supports file transport (eg SFTP), TCP/IP forwarding and even SOCKS HTTP proxying.
You also used to be able to run GUI applications over SSH via X11.