Actually all thugs are wanted by the police that's why the cops go after them. But the issue is, -all- of them are which is why cops will be focused on one and then switch focus again and again, because as another comes by it takes the cops attention away from its current target.
And BoatCrews isn't hard. I've already tested them and they work in Boats too. Biut I have Boats excluded as allowed vehicles until I can specirfically focus on the Water side of things to make sure or discover any potential issues with those.
In fact if you want you can probably go into the excluded models file and remove the boats from it and then they will likely start spawning, maybe. There are certain validations that are in place that might also prevent them from workin on water such as isSwimming or isInWater but not sure you can try and see. Just make sure any boat models that you remark out (dn't delete them just remark them out) they are valid dribable and not a boat type that will crash the game if something tries to use it.