I would envisage an amendment with beringite together with a forest revegetation in order to have a long sterm stabilization of the water and element cycle. But the initial soil conditions are important to estimate the opportunity of further nutrient amendments.

Phytoremediation has been considered the most effective way by far.

Yes , phytoremediation is most effective, but you will most likely need to have a preliminary  pot  trial using some potential accumulator plants. This will very useful to select target plant species, study uptakes rates and the phytomanagement potentials of your trial plants. Information from preliminary investigation will be helpful in managing your field trial. Already identified accumulator plants may have some site-specific characteristics that can influence their performance in your intended site. I am currently doing a  phytoremediation related research.