I have been thinking of doing this for long time, finally I managed to get this working. Here is what you need to do to get i3 with all other gnome services running.
First we will create 2 files, this is actually all you need. In these ones, I copied the original gnome files and just change gnome-shell to i3 to replace my window manager.
11:15:43=>[~]> cat /usr/share/gnome-session/sessions/gnome-i3.session