I think there are two places where the bunks can be. The 17' Spirit standard
comes with a sofa/bunk across the front of the trailer instead of the bathroom. There is also an option on all Spirit models to replace the side dinette with a sofa/bunk.
Here's a 17'er with the side bunk option: 2013 17' Casita Spirit Deluxe Bunk Bed Upgrade | Raleigh, NC | Fiberglass RV's For Sale
Couldn't find one with the front bunks. I'm thinking most buyers in that size/weight class want a bathroom.
Have you asked Casita
? Tell them what you need/want and see what they can do.