Dennis,
Your floorplan is the "travel trailer version" of our 242RL fifth wheel. We also have to run the slide out a bit to use the bathroom, so usually we stop at rest areas and just keep the holding tank empty. Easier that way.
As for wood framing, as long as you watch your roof, avoid leaks, you'll be just fine. Like I said, travel trailers have had wood frames for over 50 years and many of them are still going strong. If you read through these forums, you'll see that an aluminum frame is no guarantee of "leak protection." A number of upper level RV's have had water damage and we all have the same wood particle flooring, luan panelling on the walls and ceiling and sealant (dicor) that's used to protect the joining surfaces.
The older alumalite trailers were lighter than conventional fiberglass sided RV's, our 34' CBFK weighed in at 7600 lbs empty with a GVW of 10000 lbs. They called it a "light weight trailer" but in actuality, when you're moving 8000 lbs of "box" down the road, it's not lightweight no matter how you cut the deal. The specs on a 2001 Alumalite 28' has empty weight of 7200 lbs. Are you sure you read his weight label correctly? you may have been reading his max cargo weight, not the actual RV weight..... However, the "older" HR trailers, in the 70's and 80's were MUCH lighter, simply because they didn't have the livability features of today's units.... pretty much all they had was a referigerator, hot water heater, open air furnace, non-ducted A/C was an option, and very minimal foam mattresses, insulation, carpeting, etc. That started to change in the 90's.
What I've found in many of the "lightweight" RV's is a return to the thinnner walls, less insulation, smaller appliances, thinner carpet, fewer "luxuries" to keep the weight down. In other words, an RV equipped more like the Springdale with a "high end name" (and price).
Think optimistically about your RV, enjoy what you have, realize its limitations (less insulation, potential frame damage from water leaks, etc) and enjoy the simplistic, reliability of not having all the "options"
Sometimes "simpler" works even better than "luxury" <wink>
John