I think I've seen the kind of space you're talking about, but in some of the models that had this space, there was sometimes 3 doors to access the space. One on each side and another at the rear, which was the largest opening. As I recall, these models did not have a slide unit for the bedroom........maybe that decides which models have it. I guess my concern would be to find out exactly what is located underneath this floor space, before you go drilling into it.
What year and model of MH do you have?