OK, am I hitting a consistent bug, or does the customization terminal in the Lucky 38 High Roller Suite do absolutely nothing?

If nothing like footlockers, lockers, nuka cola/sunshine saspurila vending machines, etc aren't appearing then yes it is probably a bug.

Those are the problems.

Maybe this time I'll just install a mod that improves it, since the vanilla improvements aren't working for me.

That terminal's been bugged since release. I've found that if you move your cursor over to the price column (far right) for the improvements, you can sometimes scroll down to the one you want to buy and purchase it. It'll probably take you quite a few tries to do it, though. Hopefully this gets fixed.