I had some landscapers prep for my walkway last year. I asked them to get it ready for me to put down my stones. The cut down the sides and compacted "A gravel" at the bottom, but nothing more. I am reusing slate pavers that used to be my front porch for the walkway, but it only covers about 1/3 of it. I spaced them to be stepping stones, but on top of only the compacted gravel base some are wobbly.
I think I'll be putting down landscape fabric on top of the compacted gravel base, then sand to level the stepping stones, and pea stone to fill in between the stones. Here's the real question, would it make any sense to put down a thin layer of polymeric sand before the pea stone? I want some way to lock at least the bottom layer in place so they don't shift as much.
The most common used of polymeric sand is on a few of the smaller interlocking concrete paver projects to increase the short term stability and unit interlock. If it deteriorates, it can always be supplemented with the traditional fine sand to insure the strength and stability of the pavement.
I don't know if it is/was developed for pavers with wider joints that have far more moisture penetration. Since it may not be as permanent at the other materials, I would be hesitant to use it for your proposed use unless I saw something specific in writing.