You can now use Air Canada miles to redeem flights operated by Etihad Airways. Even better, booking with AC miles does not incur fuel surcharges. Here is the award chart:

One particularly interesting sweet spot is the Sydney - Abu Dhabi - New York routing. It can be booked on a single award ticket, and first class costs only 110,000 miles. By comparison, flying just Abu Dhabi - New York actually costs 115,000 miles...

As for the other sweet spots, we can take a closer look once travel becomes possible again.