[shorewood]

Thanks for bringing that up. How about this.

Each bridge is different depending on who describes the isle. So yes some will be rickety wooden bridges others would be large and sturdy. This could create "interesting" paths for commerce and armies though the nexus. Yes your destination is on the next island over but the shortest route which would support an army and all its supplies might take three or four islands.

edit
now nothing will stop you from creating NEW bridges manually between isles as long as you have bridge building skills. For example lets say the god Fake declares war on Phoney. And he wants to invade with an army through the nexus. Phoney can't stop fake's army so he destroys all of the bridges leading to his isle. This cuts him off from commerce and trade but keeps him safe. Fake in response builds a new bridge across the void, protected by his fliers.

So yes all isles start out with navigable bridges but if the Nexus becomes a war zone its not inconceivable that we will end up with ghost isles, places where no bridge reaches.