Etihad Guest partners with a ton of airline loyalty programs for redemptions.
These include Korean Air Skypass and Virgin Australia Velocity Frequent Flyer. Korean Air Skypass offers a reasonable redemption rate for flights inside the UAE (10,000 in economy round-trip for flights that easily cost $1,000).
I looked up Etihad availability using etihad.com.
The 'GuestSeat' column is what you want. These seats are available to partners.
However, when I called Korean Air and Virgin Australia the agents could not find any seats for any dates. You probably experienced that before – you know it's available and you try to nudge the agent towards it but while they won't be able to find availability they are ready to shoot you down with 'no seats – you must be looking for revenue seats'.
I called back another day and a helpful Korean Air agent agreed to check with IT and got back to me and said that Etihad redemptions are not available (even after a 'long sell' attempt) since partner airlines need to update their booking system. American Airlines has no problem seeing it but many partners have. So be warned – sometimes these miles are a 'paper currency'…