Yes. I removed the over-cab bed on our 1997 Lazy Daze 26.5 mid-bath and replaced it with foam flooring tiles and collapsible crates. I don't have the pictures with me to send (at the moment). I know of one other fellow who built replacement cabinets for his LD.
Lazy Daze warns against storing more than 300 pounds of anything in the over-cab area. I suspect other manufacturers have similar guidelines, to stay within the structural limits of the cutaway cab roof and cab-over floor.
2008 Holiday Rambler Admiral 30PDD (Ford F53 chassis)
2009 Honda Fit Sport