With using the glitch to fly without a mount outlined in the how to get to GM Island Post; once reaching the blue wall (while facing the wall) stop and cast a 'Darkmoon' Tiger. It appears on the other side of the wall at sea level, hop on and tada you're across the wall without being a mage.
I tested it out at the blue wall near bilgewater harbor. Will try out Teldrassil later.
*Update*
Success! So, mushroom chair at first invisible wall at teldrassil to bypass it, then Darkmoon tiger at blue wall and subsequent invisible walls = GM island for non-mages. Keep in mind you will need both items as if you try to use the Darkmoon tiger to get past the first wall and the blue wall you will die from fatigue waiting on the cooldown to reset.
*Make sure you have 30+ Darkmoon Tigers, you'll need them
* Also to be noted: this method takes a lot longer to reach the island than blinking. The chair has a 5 minute cooldown, and the tigers have a 3 minute cooldown. So be prepared and set aside time for a 1hr + voyage if you plan on making a trip all the way to GM-Island.