My new 5er has a large basement. I have seen other 5ers that have a tray that slides, kind of like a large drawer. This would be a great addition for my RV, but I haven't seen any addons for sale. Of course, no doubt that if Camping World sells them it would be triple the normal cost.
Alternatively, I have been thinking that it wouldn't be that hard to make myself.
There are 3 pair of rollers, when the 2nd set of rollers comes off the rails I stop. The ones for the 3 others have a tether cable that stops the drawer before last set of rollers from coming off the rollers. One of these days I'll get around to doing the same, maybe