Do you have a credit card or way of spending directly from your platform? For example, if I have bitcoin and trade to USD, is there a way for me to directly spend that USD, or would I need to transfer it to my bank account first?
I dont really understand what do you mean, but if I get it right, you want to contribute with fiat. If so, then you are able to do it with your USD. Correct me if its not what you wanted.