Has PayJoin been considered for integration into Bitcoin Light Wallet? There is a funding request for the Nervos-Fiber PayJoin integration at Nervos-Talk.
Your insights and related decisions might be of interest there. Has Peersyst looked into this or considered implementing it? Could these experiences also be helpful for Nervos-Fiber?
Have other privacy-preserving technologies been implemented? Cake Wallet Payjoin v2 is certainly a good guide for successful implementation.