To me, that is a major enough of a modification that I wouldn't want to do it, if it wasn't necessary. Especially on a brand new trailer.
I would have to recommend looking for another unit that fits your needs without having to tear into a job like that right off the bat. Tell your dealer what you want and don't let them talk you into something you don't want. If they want the sale, they should be smart enough to listen to the customer.
Plus, address the issue of where all of the sinks drains. Making sure you fully understand where they end up. Some end up on the ground.