If you do this, I would suggest the following:
1. Make the first version you release the mod for 1.12.2, as it is currently the most used modding version. After this, if you want to tackle 1.13, feel free.
2. If you can find a way to reuse the models and animations from the last version of Mutant Creatures, do so!
3. Focus on reimplementing all of the features from the original mod before adding in your own.
4. Make sure that once all of the original features are reimplemented, you haven't forgotten the config file! Any extra configurability added by yourself to this mod would be ever-welcome!
Those are just suggestions that I figure most if not all of the people supporting your recreation of this beloved classic mod could agree upon.