Victor Fries aka Mr Freeze will be one of the main antagonist during this film. However, he won't be portrayed as a traditional villain that poses a threat towards The Batman. If you know the source material and know who Mr Freeze truly is. Then you will understand why I am going with this direction for this character. I've always seen Mr Freeze as this complex individual struggling to have everything that he has ever wanted. He is a victim. Not a suspect. Not a full blown villain. He does what he thinks is right. He is also seeking vengeance. But he goes about it differently to The Batman. That's why this pairing works so well for this film set in Year 2. 

In terms of when it comes to voicing Mr Freeze when he's in the actual suit. Looking for a voice modulated version of that. Kind of what we see in the Arkham Games and Batman Animated Series!