Doesn't Marvelous need a support mesh to add structure for the cloth? Maybe the idea is creating the main shape, importing it into Marvelous and then doing the cloth simulation...
Personally, I'd do it all in 3ds max and then add wrinkles and folds in Zbrush. It'd take quite a bit of time though, for all the cool wrinkles. And I'd need some good references to work with too. DayZ's backpacks don't look sculpted tho, I think they used scans or Marvelous for that.