Please read the complete review of the plan as mentioned in the above thread by policywala.
My views are - As you had paid premium for four years, pay one more premium (Reason - Lots of exclusions as compared to normal health insurance policy) and also switch to Multiplier or Balancer funds for maximum returns. Also keep in mind if in future the returns of the units are not good then your sum insured will also be reduced.
You can buy a new health insurance plan or top-up plan for additional coverage.