@Cudo
I share with you the complaint about Safari's address bar/search bear isolation, and your frustration with people who offer other workarounds when your OP clearly states you are aware of other ways to do use Safari for web search and that you specifically are looking for a plugin or plist-type hack.
As Trance and other's have stated, the a SIMBL plugin called omnibar should do the trick. I also prefer os x daily's article on it, as it also includes instructions on removing it if it isn't what you are after:
http://osxdaily.com/2011/08/05/safari-omnibar-combine-safari-url-and-search-bar/ or
http://www.delicious.com/jaronsampson/safari+omnibar if that link gets moved.
Enjoy, Jaron
p.s. As to the why it is the way it is what it is: IE and Chrome have integrated web protocol address routing misses with web search because both are built by companies with major search revenues. Mozilla makes most of its revenues through sharing these revenues, mostly with google (
https://blog.lizardwrangler.com/2007/10/22/beyond-sustainability/). Since Apple has no search product of their own, I do not see it in Apple's best interest to help two of their biggest competitors, so despite it being a UX PITA, I doubt they will change it themselves. To Apple's credit, although this in general runs counter to their generally excellent software user experiences, and besides protecting their company financials, they are actually keeping Safari simpler and therefore your whole OS safer for us. The proliferation of toolbars and other, mostly unregulated, browser extensions and plug-ins have sometimes introduced additional attack vectors for nefarious forces.
I use Chrome more often than Safari myself, as with Chrome I felt they have done what good software companies do (which I consider Apple to usually be), and put user experience and adoption ahead of revenue streams for the software product (a la Facebook). On the other hand, the meme that Google wants to "do no evil" is really just PR spin. In business partnerships they play the part of a 900 pound gorilla, and there is ample other evidence that they put the bottom-line first. Like all corporations, they are legally bound to do so. Here is the latest news I have seen, but there are many other stories which demonstrate the same contradictions between public image and corporate actions:
http://tech.slashdot.org/story/12/0...-google-225-million-over-safari-privacy-abuse