Definitely NEED a twin.
Huey Racer
You say ‘But as long as you do not definitely need a twin (according to air law / restrictions / or for Offshore-Operations),...’
ICAO Annex 6 Part III, Section II Chapter 3, para 3.1.2 says that “in conditions where the safe continuation of flight is not ensured in the event of a critical power unit failure, helicopter operations shall be conducted in a manner that gives appropriate consideration for achieving a safe forced landing.”
Now we all know that a safe forced landing is not the possible probably 75% of the time in probably 75% of India (the country in the original question) and the requirement is just not observed by most of the pilots with most of the operators.
But according to your criteria you would appear to really be in favour of using a multi-engine helicopter. Or would you like to change the criteria so that it just comes down to the cost again?