@Habiki
Not getting the voyage completion credit for commendations is the only downside I know of, but that has been the norm until this update. Technically you don't even have to cancel the voyage, you can skip canceling and just vote on a new one. It automatically removes the previous voyage.
@reverend-toast
You don't have to sell to reaper's. Just an option. Reaper's don't care about the time limit, and cargo will raise your reaper emissary the same way it does the merchant emissary, so you can literally stack as long as you want with no emissary, then raise the reaper flag once you get to the hideout to sell. I can't remember the exact number of cargo needed to be sold to hit grade 5 flag but I think it's around 32.
When I stacked cargo from an ashen athena the other day I noticed a few things.
It was always DR cargo, not regular cargo (obviously) or the new pieces.
It might give me both cargo mission pickups on the same island like ruby's fall or fetcher's rest but never were both pickups on the outpost. So every voyage provided either 0 or 4 cargo to collect. If I had been sitting at those other islands, I may have been able to collect the cargo faster.
Most of my cargo needed to be delivered outside of the devil's roar. I think 1 set of cargo had a destination inside the DR but most went to kraken's fall or crook's hollow. Other destinations were as far as plunder outpost and shipwreck Bay. These destinations being so far away outside of the DR when also now being required to advance the athena voyage is ridiculous.
After collecting so much, I didn't even want to sell it. That's when I decided to go to reaper's instead of the normal destinations, I also hunted down a harpoon rowboat and invited a friend to help. We made over 600k.