Bunk Mod
I have a 2020 2750BHS and ran into the same problem you have. Your setup is older than mine but this is my change and very happy with it. I snore so the bunk is my primary bed, however being an adult was hard to get into and out of, much less not being able to sit up if needed. This mod solved my problem
The frame is made out of 2x2” soft wood and screwed into the walls. You have to remove either the top or bottom ply to access the screws and it is glued and stapled in place. I had nice paneling on the bottom and saved that for the finishing of the shelves. The upper ply came out in pieces. Once the screws were removed the whole frame was removed.
In the shop I cut the frame into the L shape I wanted (you could do a U shape) as I wanted more room than just in the middle. I had enough of the bottom panel to do the top of the shelves and it looks factory! I used a 1x4” for the trim and rounded the top and bottom edges. To finish the trim I went to Home Depot and matched the trim color used through my trailer ( it also came in handy touching up bare spots you could see and scratches)!
The storage bins fit snuggly on the shelves and so far have never fallen or bounced off!
Also the top mattress doubles on the bottom making a softer bed!
Your setup may be completely different but this hopefully gives you an idea on how to proceed! My wife and are pleased with the outcome and the appearance! Have fun, measure twice and cut once! If I decide to sell returning into original configuration will be easy to do!