We had a 2008 2350 on a Ford 350 chassis with a slide and sofa and loved it. The Ford chassis has 1,470 pounds more of cargo capability and 5,250 more pounds of towing capability. Also, my understanding is the maintenance on the Sprinter chassis is higher especially the oil and filter changes. This is something you might want to confirm.
One of the modifications we made to our 2350 was replace the barrel chair with additional storage cabinets (See attached picture). Another thing we did was add a portable storage box behind the driver's.
The sofa offered comfortable seating and adequate sleeping comfort. To improve the sleep comfort we used a memory foam pad from target. I personally find the dinette seat backs to be too straight and become uncomfortable after awhile. Also, depending on the model year there were different sofas. The sofa we had was the electric sofa that was in three sections when you opened it up. The new models have a memory foam lounger that look very nice but I do not know how comfortable a bed would be. You need to try the different configurations. Try before you buy.
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If you have an questions let me know.