Sean,
Looking at your photos, your floor plan is common to a lot of trailers with a FB (Front Bedroom). Look at the Puma 23FB or the Jayco 22FB as examples. (one of these days, I'll learn how to paste photos...)
The weird platform is where a convertible sofa/bed is generally placed. (They too can also be expensive to replace.) The space under the sofa generally conceals the fresh water tank and furnace/heater.
In the Puma 23FB, there is a full height wall behind the sofa with an opening for a sliding door to the bedroom for privacy.
In the Jayco, they have a wider opening behind the sofa and use a full height sliding curtain for privacy.
Just some ideas for layout and privacy.
Good Luck.