You do mean yeast dough? I just don't use egg. I personally don't care to use flax egg in things that should be light. Flax seems to weigh baked goods down, so I'll use it in quick breads, or potatoe pancakes as a binder, but not in yeast breads or cakes.
If you mean biscuits (unless you're UK where 'biscuits' are cookies. I quess then I'd mean 'scone' maybe?) like flour, shortening, baking powder and water (and sometimes egg) I'd just either leave egg out, or use a starch like ener-g egg replacer or just cornstarch.
I have made really good biscuits with silken tofu-1/4 cup for one egg, but it's been a while. I think I posted it on the recipe section.