I don't know about the ex-addicts being trusted with a multi-million dollar enterprise. But let's set that aside for now.

Kite power requires prevailing winds in the direction you are traveling. This is feasible over certain trade routes. As for hydrofoils on cargo ships, the speed needed of the winds to loft a heavy vessel might not be sufficient for a practical kite size. A catamaran style vessel might be more appropriate because of its stability over a broad range in speeds. For initial kite testing the catamaran would be my vessel of choice.

Active hydrofoils are definitely suitable, but the configuration will have to account for kite tugging and strain variability.

Engines would likely still be needed stabilize the system during operation and during wind out of spec operations; but perhaps the expenses associated with the kite and loss of revenue for various complications, might be worth investing in a kite system for specific trade routes.

Lofting a wet, salt laden kite might be interesting. A non-porous material that is impervious to UV would be required. Carbon nanotube technologies make the kite feasible, as well as the lightweight tow cable required.

Currently, I think the system would still be too expensive to build and maintain. But in the near future, it might become practical.

See http://www.networkworld.com/community/node/22225

Why kites, rather than sails ?

I was surprised to see kites being automatically controlled, making them a valued alternative to sails, as they catch much stronger winds. My main concern, however, is that wind powered ships can overcome environmental issues, associated with transporting intercontinental fair trade goods.