Unless your hull was *really* tall, which would pose its own problems for the ship's stability and sea worthiness, or unless you had some complex side loading contraption that required significant lengthwise hull space, it's pretty much impossible to reload VLS batteries from below deck.
If it is, it has to be for very, very, very big missiles. No, I don't think it is another VLS system either.
But another question: How many ways are there to refill a VLS-launcher with missiles? Is it only possible to refill it from deck, or is it technical possible to refill it underdeck?
It is technically possible to reload VLS from below deck, provided the ship adopts a Kirov like arrangement where, instead of a tight grid array of static silos, the VLS consist of revolver like clusters of rotary launchers that occupies a much larger be;ow deck compartment with working space.
But this arrangement has tremendous drawbacks and very few advantags, especially if the missile can be hot launched.