I've just been drawn back to look at this bug. Another way of looking at it: currently, "Emacs 24" is the default application for many text filetypes under GNOME. For many users, this is annoying, as it starts a new instance of Emacs each time.
I have configured "emacsclient" as a text editor in my system (this does not seem to be available by default), but I then still have to configure it as the default editor for each file type in Nautilus.
One option would be to offer "emacsclient" as the default, but that's also confusing, for users who don't know about emacsclient.
So again, it would be good if emacsclient were folded into emacs. I just had a look at their respective command-line options, and I can't see any that clash (where the same option is used for both programs, it's used for the same thing).
What would remain is to add options --[no]client to force "emacs" to [not] behave as "emacsclient", and decide a sensible default policy. A sensible place to start seems to be to behave like emacsclient when called with --alternate-editor="", that is, try to connect to a server, and if one can't be found, start normally (emacsclient would instead run "emacs --daemon" here and try to connect to it).
Regardless of whether anyone feels like hacking on this, I'd like to know whether it's a tractable design problem (have I missed anything major?) and clikely to be accepted. If so, I might be up for hacking on it.