Starting a build in Finland

Since the Liftfoil released its efoil I’ve dreamed of owning one. Unfortunately, can’t afford one. And when I came across Pacifimeister’s build I’ve been thinking of building one. Now the time is ready for me to start converting my Liquid force foil to an efoil. I don’t have any experience in these kinds of builds, so I’m asking advice from you more experienced builders here.

Can you give me suggestions for parts?

For safety reasons (my kids will definitely want to ride also) I want to use a duct, so inrunner motor?

Do I have to use reduction gear?

What size ESC will be big enough? Can it be too big? In terms of amps. Watercooled or not?

Are there ready prop and duct combos for sale or is 3d-printing only option?

And finally, the battery pack. What is big enough for test rides but can be expanded? My plan is to place the build first to a SUP board without fuselage and wings for first test. I will build a board for the efoil during next winter.