Sadly focus to address bar is something add-ons cannot change and it's fully controlled by Firefox.
However after few experiments I think I've found a way to achieve that (it's most probably a bug), you can now in version 8.3 find new experimental option called "Force focus on page" in Options page / Short-keys. Activating this will always focus the page.
If you have more issues, please let me know to my support e-mail.
