In my opinion this is an awful solution.

You want a urine-diverter with separate containers. Storing and handling feces is infinitely easier and more pleasant when covered and dry. Separated urine is similarly advantageous; you can store it in a lightweight bottle w/cap and tidily pour out its contents at the appropriate time and place if free of solids.

It exits your body separated, you're not doing yourself any favors mixing it all back together again.

See my reply to the parent for details.