AS DavyDD stated, check out the custom builders. Advanced RV is an excellent example, albeit expensive, with Great West and Sportsmobile in there too.
Your issue of the 2 different sleeping times is the same as us, so our ERA 70A works out well for us for the same issue. It is broke down into 2 different "areas" with 2 TV's etc so one doesn't bother the other.
To answer your 10 gallon black tank question, about 3 days max for us and most others we've talked about the issue with between dumps. The 70A ERA is very easy and fast to dump. The Leisure Travel units are easy and fast too, as they have a permanently connected sewer hose, (their B's, don't know about their C's)
Also, there is no such animal as a B+ according to Recreational Vehicle Industry Assoc. definitions. It's a marketing term that some makers are using, Leisure Travel being one of them.