The 5th gen iPod Touch (and 6th and 7th) is only 6.1 mm thick, so while I don't think just because Apple can pull it off Pine64 should be able to also, it seems like there might physically be enough space. I was going to note that the 5th gen iPod Touch is from 2012, but then it feels like much of the miniaturisation progress since then has involved removing the jack. Agree that it's probably not easy though.