well, TBH, apps like iExplorer exist. If I can find out how that can access the device's filesystem I can probably do the same and support device & sim. I'll make a github issue.
Cool. iExplorer even has a Fuse module which would be perfect except it is extremely buggy. You have to use the gui to mount, and can only mount an application sandbox not one level up. If the app is uninstalled/reinstalled they lose the plot. (They never responded to my bug reports and inquiries. The iFunbox folks didn't either - seems to be a pattern with these kind of tools for Mac.)