Overriding woocommerce payment with a token-based payment method

The project I am working is to create a platform,where every items posted can be exchanged for 1 token, instead of paying prices. To do this, I`ve tried YITH /SUMO /Woocommerce reward points plugins, and Dokan as the multi-vendor plugin. Here are the problems I encountered:

1. Among all the reward points plugins, SUMO reward point is closest to my needs, as it provide payment gateway using award points. However,in each reward points plugins I tried,points-payment is just a converted version of money payment. What I want to is simply to count the cart items, and add/reduce points in two accounts, but I don`t know the location (files) I should insert these codes into.

2. Another issue is about compatibility with multi-vendor plugins like Dokan. Reward plugins usually work on single-site environment,and i dont know what extra files I should modify if I want to apply the above modification to work in multi-vendor environment.To prevent large-scale malfunctions, I think it would be wise to ask for guidance first. If anyone have had experience in similar cases that want to share with me, I would be grateful to listen to and learn.

Thank you for your reading!