$M$ is a Turing machine that halts on all inputs implies L(M) is recursive.
Now, L(M) = L' for some undecidable language L'.
So, this means L(M) is an undecidable language. But L(M) must be decidable as $M$ is halting on all inputs. So, there cannot be any such $M$ making $A = \emptyset$ which is a regular language.