I've never made vegan white chocolate, but obviously the key issue would be the need to swap out the milk powder with a vegan ingredient. From what I understand soy powder is the usual choice. The taste would not be equivalent, but this is often the case with vegan foods. You'll have to experiment to get something you like.
As for the sweetner, I'm not sure why you are planning on using coconut sugar. If you are doing it to avoid the bone char issue you can accomplish that by simply going with organic sugar, since certified organic sugar cannot be filtered through bone char. Also, I'm guessing that organic sugar is less expensive than coconut sugar as well as easier to find.