That was one of the first things we did to our 07 C190P Roadtrek, and basically just removed the internal fresh tank because it was such a horrible design. At the time we weren't sure if we would need to build a replacement or not, and over the years really have not had an issue with just using the underbody 14 gallon fresh tank.
The design issue was that in the early Chevies, before the 2007 model update to the new roof style and kitchen, plus some other changes, the furnace was in the rear of the van in passenger side bolster. The internal fresh tank was there also and molded to kind of wrap around the furnace. Great design for the cold weather claim they have as the tank was inside and got heat from the furnace to some degree. This made for a very odd shaped tank. In the redesign, Roadtrek moved the furnace to the front armoire just behind the driver seat, which IMO was a good idea. What they didn't do was make a different internal water tank, continuing to use the odd shaped one. They kind of turned it around to a different position and stuffed it back in the bolster. What they wound up with was a tank that had the volume of maybe 1/4 of the bolster was using up maybe 90% of the bolster volume. This is prime inside the van storage so have all that wasted and unusable space seemed very silly to us. Our bolster only had about 3 or 4" of space in the very front of it, with all the rest mostly air but blocked by the tank and unreachable. The bolster is actually quite larege when cleared out. I did leave all the plumbing in place, capped and under the floor I added to bolster. I doubt we will ever put a tank in to replace the capacity of the one we took out, as we carry two 2.5 gallon collapsible water jugs and have never needed them to bring along extra water in the decade we have been using the single tank. They are handy for bringing water to the van if we want to fill the tank and the only sources are unhoseable faucets, though, or to use outside for whatever use.