Hi,
When you edit a payment method in the HikaShop backend, you can assign the payment method to a specific vendor.
At this moment, you can put a vendor and change the commission mode to "commission - vendor paid directly".
The vendors can't edit (yet) the payment methods from the front-end but we are working on that.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.