Well, nothing, but my guess is that it needs to work straight out of the box for military use, you can't be hot-gluing buttons and cables on equipment that's used on a submarine.
Why not? Have a professional supplier handle the mods to mil-spec and you have a mil-grade product. If it fits the requirements you shouldn't just rule out something just because it sounds DIY.
The process might double the price, but still cheaper than anything custom ordered. Glue is a perfectly acceptable solution if done right. Plastic welding is also an option.
