In the past, we have had TSA people just zip the bag back up without attempting to brace or resecure the AL40s in the same manner that they were carefully put in the suitcase. One time this caused a jar of coffee to burst.
As illustrated, many larger roller bags have a set of parallel reinforcing rails underneath the suitcase liner. This is a general purpose Delsey suitcase. The dive dedicated ist bag also has similar rails. The AL40s are secured between the rails by fastek 2 inch buckles with webbing underneath the frame. This keeps the AL40 from shifting during transport, particularly if the suitcase is mostly empty. The buckles are easily released and hopefully the TSA guys will take the trouble to rebuckle them after removing the tank for inspection.
Of course, you can’t fit much other gear in the suitcase if you want to stay under the 50 pound limit.