Islands for ships only

Since 1.2 patch the A.I. extensively uses it's island for militia, wich hurts it in multiple ways.

Now I can live with level 3 barracks units being trained there as the island will have a more sustainable population and any recruitment done there may actually help the A.I.

So what needs to be modded so peasants militia and level 2 barracks units can't be trained there.

I've also bee thinking of making certain towns ships only at certain locations until the town developes. This would help force the A.I. to build a defensable navy, while letting the population grow. I was thinking 1 town for each faction that doesn't have an island.