There is already a scheme that allows you to exchange this way: the one who wants to withdraw the cryptocurrency to the fiat money must lock it in the platform , then the second participant transfers the fiat, and both confirm the deal. I'm not sure exchanges will happen this way on this platform , we need to check it out .
It is unlikely that fiat will be introduced to the platform, the website has the exchange scheme described above, ie the money will be transferred through external payment systems.