Well, you can always swim. But if your island does not have any nearby open bindstone/banks, getting attacking peeps back to the fight after they die might be a tad difficult.

AFAIK no SB style summoning or UO style portals are in, so assaulting a small isle might be difficult if the defenders are on the ball.

But, having natural defenses and chokepoints can theoretically enable a smallish defending force fight against a huge attacking zerg.

So, we will see how it pans out.