Is Normative Ethics Richer?
1. Are western traditions innately richer because they have the moral ought?
My answer: No. In fact, in my book on ethics I will prove the following: the non-normative ethics are richer: Under specific assumptions, in limited conditions, one can derive a normative ethics from a non-normative one. The relation between non-normative ethics and normative ethics is analogous to the relation between Einsteinian theory and Newtonian theory: under specific assumptions, in limited conditions, you can derive the Newtonian theory from the Einsteinian theory.
2. “Uchit” and “Unuchit” do not function as ‘ought’ and ‘ought not’ do. They mean something like appropriate and inappropriate. That we have different words with different meanings to pick out the moral ‘ought’ and moral ‘ought not’ suggests (merely suggests!) that, perhaps, there is a greater richness to our ethical languages than those governed by the moral ought and moral ought not.
3. We can neither map the moral imperatives (let me call the ‘ought’ and ‘ought not’ this way in order to avoid using scare quotes to mention these words) at the phrase level or at a sentence level. What we ‘map’ are the ethical nature and the ethical force of some statements in some context or the other.
4. Yes, many systems of Deontic logics make use of one or another version of modal logics. They enrich the propositional and predicate logics with deontic terms (which the moral imperatives are) and allow us to track the logical and semantic behavior of these deontic operators.
5. Decidability presupposes expressibility and, as you say, the converse does not hold. (See ยง1.) The trade-off between the two depends on what human situations require: a decision-procedure or a learning-heuristic. The western ethics sees the ethical event as one that requires a decision procedure; it is my claim that in our traditions an ethical event requires an action heuristic.
6. Which is better? This does not depend on the semantics of ethical languages but on what ethics is supposed to do: teach you how to act ethically, or decide which type of action is ethical. In the latter case, you still have the problem of performing the ethically correct action.