BB, be very careful about long term storage in take down cases of almost any sort. Moisture traps. I've seen more than one newish English Best in for rust removal requiring complete new bluing and CCH because the owner thought storage in the case was fine. You were on the right track being concerned about air circulation into the barrels. Astounds me that after paying over $100K one wouldn't learn how to store it properly however......
I am in the camp that would not consider using Tru-oil as a "barrier" to protect the wood finish of a gun stock. I am about to refinish a stock on a Husqvarna using Tru-Oil. It will be the Tru-Oil finish I am looking to protect when wax is eventually applied.
I put silica moisture absorbents inside the take down case I use but now I'll put in several and keep an eye on the situation until I'm sure there isn't a problem- I haven't had that case for long. The safe is already desert dry itself, so that's not an issue.