This will NOT affect your reputation towards goblins in Outlands, just Azeroth. Goblins in Outlands will treat you normal.
Not many know you can actually gain rep with them, just that there hated by you because of Steemwheedle Cartel quests and such. Well you CAN get rep from them even though it is tough and you can also get reputation rewards. Rep rewards would be a full pirate suit set at Neutral, and then the fabled Bloodsail Admirers Hat which i've been told only about 300 people SERVER-WIDE have this (this was some time ago it may be a little higher) so if your up for producing a server first this is a good way to do it!
Basically whats going to happen is your going to need to kill booty bay guards.....lots and lots and lots of them. Each guard gives 25 bloodsail reputation and -65 Rep in Booty Bay with a smaller splash to all other goblin cities (the -65 rep needs confirming, it may be higher)
So if your coming from 0/36000 hated with Bloodsail, thats 1440 guards JUST to get you out of hated. You then have Hostile(3000), Unfriendly(3000),then Neutral(3000) Which would be 360 more guards to get you all the way into friendly, so expect somewhere close to 2,000 guards to kill to get there.
Now your probably thinking "this is useless...hated by steemwheedle cartel, long ass grind, boring as hell, and almost no pro's" your right its tough, but if your a perfectionist then you would be up to the challenge...not to mention the parrot you can summon with the hat is unique (called a Blood Parrot)
Link to the item: Bloodsail Admiral's Hat - Items - World of Warcraft
You will have to get a quest from a captain on one of the bloodsail ships outside BB when you hit friendly in order to get the quest to get the hat. You must go into booty bay and kill the two leaders of it (they are on that piece of boat sticking out at the top of the building by the ally flight master)
TO GAIN YOUR REPUTATION BACK:
There are cloth hand ins at each steemwheedle cartel city. Ones linen, silk, mageweave, and wool
You have to turn in 40 of whichever one along with 4 of a certain item and it will give you +500 rep to that city and a 350 rep splash to all others. The easiest one if linen of course, it takes 40 linen and 4 empty vials (alchemist regeants).
Overview:
-Kill ~2,000 Booty Bay Guards
-Become hated with all of Steemwheedle Cartel
-Get quest for hat
-Kill the two leaders of Booty Bay
-Profit
Not the most immersive guide but since this reputation isnt that complicated you dont need much of one.