I'm not an expert here, but, as a chemist with a strong gastronomic interest (and a penchant for waffles), can suggest some things which may be helpful. Lye is a caustic alkaline solution, traditionally KOH, and more commonly these days NaOH.
First, my understanding of lye as an agent in cooking is limited to its use in pretzels and "laugen" bread and ramen soups. The pretzel making process involves a final dipping of the dough in a lye solution in order to promote the Maillard reaction during cooking; this is not the same as the leavening process. Ramen noodles are a type of "alkaline noodle" and I believe use the lye to break down the gluten to make the flour more pliable and less elastic. Again, not the same as the leavening process.
The use of lye as a leavening agent comes from taking lye (produced by washing fireplace ash) and boiling with lard to produce potash. The purified version, pearl ash, was one of the first chemical leaveners used in the kitchen. Pearl ash acts as a leavening agent by reacting with an acidic ingredient; fruit juice, sour milk or molasses, to produce CO2.
So to answer your questions:
I can't see how it would make your waffles fluffier than conventional modern rising agents, even if you did get your chemistry right. You still need to get your CO2 from somewhere and substituting your bicarb for lye actually removes this element. You would need to rework your entire recipe, I think.
Yes. Without doubt. More than likely it will degrade the taste of what should otherwise be a delicious dish. Alkaline foods are well known to have a bitter after taste (think kale and broccoli). Even scones made with a little too much baking soda can leave your mouth tasting and feeling like you've just had your annual clean and scale at the dentist.
While lye is used as a cooking agent in some instances, even the food grade solutions are extremely caustic, and, undiluted, are actually classed as poisons in some instances. It is corrosive to the body, especially mouth, throat and stomach, and can cause serious damage to the eyes. This may be stating the obvious, but best to assume ignorance and work up from there. Apart form mooncakes, I am not aware of a dough recipe (or anything else for that matter) that incorporates lye within the dough itself. Unless you have experience handling this ingredient in the kitchen, alternatives are recommended. I cannot tell you how you would determine whether your 'lye reaction' is complete within the dough; certainly gauging the completion of 'the rise' would not be sufficient, and the cooking process may need to be adjusted to accommodate this. Mooncake dough, for instance, is allowed to sit overnight, and even for up to 3 days before cooking. Too long to wait for my waffles!
For your interest, there is a very good comparison of various traditional and modern leavening agents here. Interestingly, the author concluded that the best agent overall was baking soda. Just like modern research chemistry in the lab - someone has done the reaction already.
