It seems to me there are many redundancies and infelicities in this scheme. That ~N and ~n yield chars in different vargas, for example, or that prepended ~ (that requires shift on most keyboards) is used instead of ; (that does not require shift and is therefore much easier to type for the common ś character. .Dh is a redundancy - two codes where either .dh or Dh would be enough. Etc.
Maybe I've misunderstood. I'm not even sure whether you are aiming at Devanagari output, or one of the other schemes like IAST.
Dominik