Why existing boats?
Because they exist! The entire existing fleet will have to rapidly reduce its fossil fuel consumption and associated pollution. The processes that will be validated on the coasters of the project may be reproduced on other boats. In the meantime, hybridizing an existing boat, for example by adding auxiliary sails or parallel hybrid propulsion, is still reasonably priced and allows you to calmly study the economic profitability of the project
Why a hybrid boat and not an “old rig” or a sailing coaster?
Because cabotage from port to port requires a certain regularity that is not very compatible with the vagaries of the wind. In the “worst case” (which must always be considered), it is necessary to have a completely reliable backup solution. Parallel hybrid propulsion, for example, makes it easy to add an electric motor to the existing engine, which opens up the question of producing electricity on board a boat.