Ed: you should try ( and provide feedback to ) Firebug 3, they're dong exactly what you described - implementing Firebug UX on top of Firefox Devtools:
I tried it early on, but it was unusable. I should really give it another go, yeah.
I really dislike how laptops (MB[P] or other) override the function keys with the laptop controls. I know you can usually set it to be Fn+F<key> to do things like volume, brightness but I think the function keys should keep their original uses first.
Yep, function keys were sacrificed so that manufacturers could drop dedicated keys for functions like volume and brightness. I personally think it was a good move, but as a consequence I rarely use the Fn+F* key combos in applications and my apps don't bind to Function keys.