How environmentally sound is it to use wind energy, to artificially produce hydrocarbon gas, which then would presumably later be burned in these fuels cells? Surely this is not solving an environmental problem, but creating an extra source of emissions in the long run?

Maybe not? Is the CO2 used to produce the methanol taken from the atmosphere? In that case, the emissions from burning would only be carbon neutral. Perhaps this is a better method of carbon sequestration than it is a fuel source?

As a merchant sailor myself, I would love the opportunity to use the wind in merchant navigation again. However, sailors would have to be trained extensively to use this method. Also, Using the old trade routes of sailing vessels would mean a drastic re-shaping of the type of traffic in cross ocean shipping lanes. Consideration should be given to vessel maneouvreability, as a lot of small and vulnerable sailing vessels using the trade winds and so on would be seriously impaired by large merchant traffic.