Plenty of fruity normally aspirated Duratecs out there. Caterham seem to have done plenty with it and seeing more and more MK1/2 Escort rally cars with them now.

Guess it depends what you want ultimately. If you want a billion horsepower and a turbo, a Zetec might be the easier option as it's well proven but, if you want something normally aspirated and 200-250bhp, I would think the Duratec is the better option as it will always come with the bonus of the weight advantage.

A combination of bits from a Fiesta ST, Mondeo MK3 2.0 and the US Focus with the Duratec lump, I would imagine that physically fitting the engine would be pretty cheap/easy.