Typical RV construction uses roof trusses that span from side to side so no supports are necessary to hold up the roof. If you look closely that cabinet/wall that you are looking to remove is probably framed with 1x2's and covered with thin paneling. Highly doubtful that the wall is structural.
Here is your floorplan:

Here's the floorplan for the 2013 S-225RBS, which is only 2' shorter than yours (26' vs 28'):

I would think your biggest issue is going to be replacing the two accordian curtains with one big one to close off the bedroom. Our old Sunnybrook had a big pleated accordian curtain that went all the way across like the 225RBS.
Our current trailer came with sliding doors on the front bedroom:

I had the same issue with bed length (I'm 6'5") and we were able to gain extra room by removing the sliding wood doors and putting in drapes that DW made. We actually like the drapes better because they absorb sound rather than reflect it, and the dog can pass through easier.