There are many possibilities, but don't begrudge SE if they implement Hamlet Defense using known and pre-existing enemy forces and critters first.

We know what Serpent Reavers look like, so it would not be difficult for the SE development team to create content with them attacking Aleport. But I've yet to see a Sahagin, personally. I don't even know if their models are rendered yet. So it might take longer for SE to develop content with them attacking Aleport & Wineport.