What are the benefits and disadvantages of a master group or blanket policy instead of individual policies for commercial habitational?

This appears to be a question about CONTROLED INSURANCE PROGRAMS, if that is what your are referring to. These type of programs are designed to a lower pricing for the project. It also serves to lower the risk to a project. However they are mainly used on large construction projects that warrant the use of these types of programs. It is a massive undertaking to get the economy of scale to cover the cost of developing the program. Premiums can range from $750,000 up. If you are considering a large project you should consult with a large insurance broker that can put together such a program. Their services WILL NOT BE CHEAP.