Alright so I spent some time trying to figure out a way to get to GM island on my Mage, found out I could port out of the barrier then slow fall back in and drop fatigue.
Can pretty much do that endlessly (don't do it in corners, you get stuck) gave up trying to find a way to mount up on the otherside, but this gave me the following idea...
Have a mage use this port in and out glitch to get to the shortest route between the barrier and GM island. once at said spot, you summon a goblin mage there and have him fly up as high as he possibly can, right before fatigue kicks in he blinks past the barrier and rocket jumps + slow falls to GM island /profit.
Would try this myself but I don't have a goblin Mage =\ or do I have any clue on which area would be the shortest travel time.
Edit: Now that I think about it, should only need 1 goblin mage to do this, I'm dumb.