Sorry, but I'm not sure I understand.
What do you want to achieve with WinSCP? WinSCP also has username/pw in its script file. So you can update the password the same way as with PSFTP. Or what is the problem?

Our current setup involve in using PSFTP with the username/pw in it so we only need to update that one file, let it sync and good to go. This is useful for when we have multiple sites and not have to worry about logging into each to update the passwords.

Can this be acheived with WinSCP?