I purchased a Pelican 1615 Air case.
I wonder a liveaboard would frown on a hard case like that, as it doesn't stow very compactly? Anyway, we have two soft-sided roller bags that we have used on many dive trips, so ideally we would use those.
If you are going on a liveaboard, your problems might be solved automatically. Some liveaboards carry rental wetsuits. There is a good chance they will have vinegar on board. Ask them about both.
You cannot carry any liquids? Why not? If you took a bottle of an alcohol/vinegar solution for ears, it will work fine on your P-valve, too. You just need to bring enough for both.
Without any kind of a vinegar solution, a very thorough fresh water rinse for the P-valve should work for a week-long trip.
Whether I bring a backup wetsuit or inquire about the availability of an emergency rental, it feels like an admission of what every drysuit owner knows: a suit WILL develop a leak; it's just a matter of when. <sigh> If rentals are only available by prior reservation and payment, then it's a question of which costs more: paying the liveaboard for a rental, or paying the airline for an overweight bag.
As for the vinegar, my concern is that liquids are bulky and heavy. At home I run the vinegar and water solution through for about a minute, which uses a lot of vinegar. Someone suggested buying some locally, which makes more sense than trying to bring it in checked baggage from the US. If I can find it easily, that's great, but I would rather not spend my days before the liveaboard hunting for supplies in Egyptian grocery stores when I could be out sightseeing.
Since you're on the Aggressor, you'll be in a cabin with a shower - ask for an extra towel and put it over the shower curtain rod, then drape the drysuit on it. Make sure the zipper is not folded over when you drape and hanging without any pressure on it. I saw a few divers do the same thing with a towel but on one of the outside boat railings. They secured it in place with bungee tie-downs cinched around the middle of the suit.
Draping it on a towel over the rail seems reasonable. I can't really picture the bungee arrangement, though. For drying undergarments, I am planning to bring some of those large plastic clothespins that are used for things like keeping beach towels secured to chairs.