Hello,
So you don't want to restrict "collect on delivery" and allow it for all of your vendors.
But I suppose that, when your vendor will be paid via that payment method, they will receive the money directly from the customer and then would have to pay you back you fee, right ?
Regarding Paypal Adaptive restriction, we do have two ideas of features which could feet your needs.
One would be an option to not display Paypal Adaptive if the vendor does not have the paypal email configured.
Another would be a restriction on the vendor group, like we have for the shipping methods.
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.