I'm not sure you have mentioned, but are you not taking your bike with you? In a box?
If so, then just put your panniers in a cheap light duffel bag or something. How many panniers are you taking, two or four?
I have always carried my handlebar bag over my shoulder with the usual valuables in it, and even taken one pannier on as a carry on if needed.

The obvious reason I ask are you taking your bike is referring to if it is boxed, then you can easily put a tent and sleeping bag in with the bike (well, maybe, I have in the past).

Perhaps before mentioning more ideas, should wait for your response about if you are taking your bike and how it is going.

re pumps, I have been happy with my Road Morph G (gauge) as it works very well pumping up to over 100psi and is not overly large or cumbersome, plus it fits easily into one of my rear panniers (dont like the idea of having on my frame either).

I guess the only advantage to these type of bags vs a suitcase is the option of riding away from airport (but then always touches on getting a new box when returning).
I would say however that these type bags probably can hold more as they are more "odd" shaped.
I have always maxed out what I carry on my self, helmet etc stuff that is more fragile. Plus I have been able to put front panniers, tent etc into the bike box, limiting what I have left, usually rear panniers.