Analog film photography and cameras

Meh, if every second or third hipster on the planet bought one and a single roll of film to put through it, that'd be a lot of sales of film which can only be a good thing.

Fair enough.

Getting someone into a 'proper' camera would probably generate a more sustained string of film purchases (which would be better)

Excacly.

but new film cameras are few

There are myriads of good, used 35mm film cameras avaiable on this planet.
For the price of the "Konstruktor" kit you can get a used, say, Canon FD body & prime in good condition,
which surely is far superior in every aspect (but for the fact you can't assemble it yourself like a Kinder Überraschung).