Can you add yeast to buttermilk biscuit mix and let it rise to add lift?

We added it in proportion and they rose perfectly and the consistency only changed slightly.

That would make them "Angel Biscuits" a blend of the best of biscuits and buttermilk dinner rolls. you would mix the biscuits with the instant yeast and let the mixture rest in the refrigerator for 2 hrs and then bake at 450 for about 12-15 minutes.

That would make them "Angel Biscuits" a blend of the best of biscuits and buttermilk dinner rolls. you would mix the biscuits with the instant yeast and let the mixture rest in the refrigerator for 2 hrs and then bake at 450 for about 12-15 minutes.

Could you replace some of the liquid called for in the recipe with carbonated water?

If you do this, it won't be biscuits, it will be rolls. Is that the result you are looking for?

Yes. Mix 2 and 1/2 cups of baking mix with 3/4 cup warm water and 1 packet of yeast. Knead a minute or so. Shape into rolls as you wish. Let rise on a greased pan. Bake at 400 for 10-12 minutes.