Wind turbine industry is growing and future predictions are promising. However, a shortage of installation vessels could influence this growth in offshore wind industry. Commonly, wind turbines are installed in components using a jack-up vessel. Occasionally, wind turbines are installed fully assembled. Lifting above the wind turbine is not necessarily for fully assembled wind turbine installation due to the center of gravity of a fully assembled wind turbine. Wind turbines can be installed fully assembled using cranes in twin lift configuration to reduce required lifting capacities. The flexibility and scalability of the vessel depends on the location of the cranes on the vessel. Different vessels can install wind turbines with their advantages and disadvantages. A morphological analysis in combination with a comparison are used to identify promising solutions for fully assembled wind turbine installation. One new concept, the PWT installation vessel, shows overall improvement in installation rates. This solution, developed by the author of this paper, is proposed for flexible and scalable fully assembled wind turbine installation. Furthermore, this specific vessel is usable for other installation activities too.