Although I'm no expert, especially compared to the folks on this site
, I redid our cabin sole earlier this year and am pleased with the result. There used to be a product made specifically for this purpose that was very popular, but they apparently went out of business.
I did a light sanding to get rid of gloss, dirt, etc. and refinished with two coats of semi-gloss exterior polyurethane. It is holding up well, not too slippery when wet and looks good.
I would suspect that you will have to sand the cetol back to wood--very carefully as the veneer is thin and you don't want to sand through it.
Others may have better options.
Frank