Chris,
I'm bidding one now similar in scope to yours in all ways except for the plaster issue you are facing so I'm not sure I can be a whole lot of help here. My only question is if you aren't tearing out the plaster, how do you plan on properly insulating the room. As far as the kerdi goes, I have always applied my vapor barrier on the warm side of the insulation so I'm also not sure the kerdi would perform the way you would need it to in this application. Also watch out where you are ventilating the cooling unit. Depending on the unit, you need to ventilate into a space equal in size or larger than the wine cellar itself but I'm sure you already knew that.
I will be interested in what others have to say on this subject but that is my initial reaction.
I'm bidding one now similar in scope to yours in all ways except for the plaster issue you are facing so I'm not sure I can be a whole lot of help here. My only question is if you aren't tearing out the plaster, how do you plan on properly insulating the room. As far as the kerdi goes, I have always applied my vapor barrier on the warm side of the insulation so I'm also not sure the kerdi would perform the way you would need it to in this application. Also watch out where you are ventilating the cooling unit. Depending on the unit, you need to ventilate into a space equal in size or larger than the wine cellar itself but I'm sure you already knew that.
I will be interested in what others have to say on this subject but that is my initial reaction.