If it can be done on a small civil machine (MD 902) why can't it be feasible, from a design point of view, for a larger helicopter?
In short, I don't know.
I've not wrked on any of the MD products so cannot say if or why not. Off hand though, it would most likely do with the weight of the structure versus the AUW of the final machine versus expected payload/range/cost with cost probably being the decider as always.