Would someone post a picture?
I'm trying to picture this. I think I've seen these but don't know which one. There's a style that puts sliding storage trays on either side of the underside spare tire carrier, and there's another style that is mounted inside the Monty basement where the items sit on the drawer, then instead of having to reach in get your stuff you use the drawers to slide the contents out making it easier to retrieve stuff. This might slightly increase the height of the basement floor but the tradeoff in convenience would certainly allay that (I think that's what pineranch alludes to.
For the outside one I hope it can be locked. For the inside the basement one, I hope it can support lots of weight (several hundred pounds) and in itself doesn't weigh so much. I'll have to go search the internet. I'm not having a problem retrieving stuff since our outing frequency is so low right now, but I can certainly see for more frequent use owners this is a great idea.
On Edit: Wow, I found these pretty quick, but you get the idea: