I have been thinking about this since I am interested in a long range cruise aircraft, with endurance of 12+ hours. What about a seat with a velcro seat cushion. When needed you peal off the padded cushion and under it is a kind of toilet seat with a recess in it shaped to accept a GladWrap 1 quart container that can be sealed after use. Use it, seal it, put the cushion back on. If needed twice for a long flight you can put a new empty one in the recessed holder in the seat. Anything like that already on the market? Perhaps I ought to patent the idea. Only problem is, sitting on the velcro.
But I think I could figure something out for dealing with that.
I have a little urinal in the plane now. I have not used it yet. The last long flight, I was so ready to get down.... I was VFR on top, delayed, looking for a hole to get below the layer, and getting very impatient. At some point you either have a mess to clean up, or you make some imprudent choices, if you don't have some way to deal with this. I wonder how many accident reports have this as a contributory cause. I made the quick run to the restroom, but it was a near thing.