If those new files are at the end of the list of opened files, it should work, because the way Talefish saves the progress is quite simple (some might say stupid). It saves three values of each directory already played, of which only two are really relevant to setting the progress:

• current index (number of the file in playlist played)
• duration played in file
• percentage played in directory (this is only used to display the percentage bars in the open dialog)

While this means you may get weird behaviour if you choose to reopen a directory with different sorting, you should be fine just reopening the directory when adding files at the end. I hope this helps as well.

Well, qml is not a bad thing in general. Actually I think it's really nice to do user interfaces and some other things with it. Directory based media handling, for example, sadly is not one of those things*: I haven't found a nice way to query file durations (or any way at all to get file meta data like ID3), so if you open a directory, it has to open each file and hope that it's a valid format that is read within the limits of a "watchdog timeout". For large directories that's taking a while and may even trigger the systems crash handler dialog.
Basically, opening files and searching for matching covers (easter egg: you can put different jpgs named somehow similarly to the corresponding audio files in the opened directory to match them) is just a bunch of more or less dirty hacks put together.

Also: Kudos for trying to port your device!

*) I really would like someone to prove me wrong here!