I would love to see payment methods supporting a cost, just like shipping methods can have a cost.
Here in our store, Cash on Delivery is used quite alot (40%). This is an expensive service from our postal services that we have to charge for. Without a cost connected to the payment method, this will be a challange to implement.
We created issue for this requirement https://github.com/VirtoCommerce/vc-community/issues/457 you can track progress there.