Hi,
I am looking forward to the arrival of my Pi3B+. Based on the blog entry https://volumio.org/raspberry-pi-3-b-plus-audio-review/ , the USB packet loss issue is a thing of the past, unless the Gigabit-Ethernet connection is active.
How about introducing a non-sticky Ethernet disable? Is this possible by e.g. disabling the driver? Disabling the Ethernet should eliminate one packet loss cause - the only USB device remaining in most configurations would be a DAC.
By non-sticky, I mean that a simple reboot should re-enable the Ethernet, in case there are problems with the wireless connection.