If I have a single window on a virtual desktop of its own, I think it
should be "activated" when I change to that desktop.

In other words: When I change to a desktop with a single window on it, I
would like it to behave as if I had click the windows titlebar.

Perhaps it should be so that the last active window on a desktop becomes
the default active window when you change to that desktop - unless of
course other things occur that take higher priority, such as the mouse
cursor being over another window in "focus follows mouse" mode.