"open" mode with "save as" UI?

[GNUGradyn]

Hello! I'm not sure if the device APIs allow this, but it would be nice if we could prompt the user for where to save a file like with "save as" mode, but then write the file like with "open" mode instead of copying from somewhere else. I am making an app that allows creating backup files that are quite large, so creating the file in app data and then copying it to the user space would be quite expensive storage wise and take alot longer. It would be better if I could create the backup file directly in the user space where the user would like it to be saved.

Thanks!