This is an external airport gateway: Friedrichshafen Airport (Germany, gateway to Liechtenstein) is in Germany, not Liechtenstein. The rental contract must permit the onward international journey and every transit country.
FDH is in Germany. Check the planned drive through Austria or Switzerland and obtain permission for every country, suitable winter equipment and a confirmed return at the actual branch.
The airport states that rental providers have counters in the terminal. Confirm your supplier, desk hours and vehicle area, and arrange the cross-border journey in writing before departure. The airport’s location in Germany does not imply permission to enter Liechtenstein.
A car can be useful for an Alpine regional stay, mountain accommodation or a journey that includes neighbouring countries. For Vaduz and other towns linked by buses, compare public transport before renting for every day. Parking, border permission and the roads actually used matter more than the country’s small dimensions.
Compare airport collection with a later collection if you start with a city stay. Include the transport to a different rental branch and any extra parking nights when comparing the total cost.