Recent innovations in online, social and interactive media have led to the emergence of new forms of documentary, such as interactive documentaries ('i-Docs'), with qualities that lend themselves to more open and inclusive production structures. Still, little is known about the experience of making and/or participating-in these kinds of documentary. Our two-year in-the-wild study engaged a large community-of-interest in the production of an i-Doc to explore the ethically-desirable yet challenging aim of enabling multiple subjects to have agency and control over their representation in a documentary. Our study reveals insights into the experiences of participating in an i-Doc and highlights key sociotechnical challenges. We argue that new sociotechnical infrastructure is needed, that frames both "executory" and "structural" forms of participation as symbiotic elements of a co-design process.