So I actually tried this a week ago after discussing it with another forum member and the results were "good" if your only concern was keeping moisture out via a vacuum sealed barrier.
View attachment 3260
I used an empty amo T60 vial shoved into a cut to size vacuum bag and sealed with my food saver tool. Did it work? Yeah. Would I do it for every vial? No. It's too much work for what I consider not a lot of benefit and the biggest sin of all, it doesn't fit in my nice little foam case.

I have elected to just put a desiccant bag in the case where each type of pep is stored and call that good enough. Moisture intrusion should be pretty identifiable if it is any amount worth being concerned about and unless you are freeze/thawing all the time, any good deep freezer should eliminate the majority (or all) of this issue.
EDIT: I was going to suggest the reusable desiccant canisters like you would use in a gun safe or storage locker but I am not sure how effective any of that stuff is below freezing. I had some so I tossed them in there but it might end up being a waste of money in the long run.