Can you turn into dark jak on jak and daxter the lost frontier

No, you won't be able to transform into dark jak in the lost frontier. According to the game, eco is now unstable but oddly you will be able to transform into dark daxter. Though you cannot transform into dark jak you will be able to use your other eco powers like in the precursor legacy. The game does not reveal why jak cannot transform into dark jak and fails to even mention anything about light jak.

You cannot turn into dark daxter at will, and the major hint for a dark daxter mission is if jak and dax get seperated. He transforms into his eight foot tall dark form when pure, liquid dark eco pours on him. That's why you can be dark dax.