We had one in a pop up and loved it, but as stated above, you'd have to cut a hole in the outside of the van, unless there are other styles of cassettes I don't know about. I like the outside hole so you can empty it without the possibility of a spill in the van, but I honestly can't think of another reason why a porta potty wouldn't work as well or even better due to the option to remove it when not needed. We remove ours in the winter and throw it in the garage so we don't have to winterize it or anything. Also, every now and then, depending on our site and privacy, we just take the porta potty out and sit it outside the van. We have also put it in a tent (a big tent) for the ladies nightly duties a time or two. Lots more options with a porta potty, IMHO.............