If you are full-timing, I would avoid the "lightweights", as their insulation, frames, axles, and many other items are indeed lightweight.
They don't even have roof rafters!
We have a 28 foot Flagstaff (really 31 feet), and I wouldn't full-time in it. We bought it only because it was light, and we don't use it heavily.
You might have a hard time finding a fifth with seperate toilet and all of the other features you want, as it seems that the manufacturers are going more toward a fully-enclosed bathroom.
You may also want to consider a slightly longer trailer, as there are many that still come in under 10K lbs, and many of them have a bedroom slideout, which gives you so much more room and storage.
The Sabre 32RCTS is at the top of your load range, but would be an awesome full-time unit. The Sabres are very well built. The 31RLTS is also very nice, although it appears they use lighter axles, as the load capacity is less.
And even though this is a Forest River site, don't rule out the other makes. Keystone has some very nice fifths in that weight range, the Cougar High Country fifths with the "helium" construction especially so, and they have thicker walls than some, thus better insulation.
I would suggest spending a considerable amount of time on the internet, researching all of the different models and their features. If you are going to full-time for a year, you will want something that is comfortable.
Once you have a few fifths picked out, go and see them in person, as that is the only way to be sure of the quality. Pull out drawers, look inside cabinet boxes, compare frame sizes and axle weights, and don't be afraid to ask questions.
If you don't mind shopping, picking out a new camper can be lots of fun!