Payment methode reservation, paying 20% of the full price

-- HikaShop version -- : 3.0.0
-- Joomla version -- : 3.6
-- PHP version -- : 7

Hi guys,

I have a client that wants the possibility that if a product is ordered from outside Europe and it is more than x kilo's that the payment option comes "make a reservation".
So somebody can reserve the product and pays 20% of the product to show that he is really interested.

Is this something that is already possible or something to make in a custom payment methode?

Thanks!