First off there are DVC studios that sleep 5 (w/o an air matress). Second, the DVC Studio rooms are the same as the regular rooms, so if you are going to bring do the air matress route you could either way. 3rd, if you don't want the kitchen you could always book 2 studios. 2 studios is cheaper than a 2 bedroom.
There are DVC ONE BEDROOMS that sleep five, but no studios.
The DVC One Bedrooms that sleep five are BLT, OKW (renovated rooms), AKL (some one bedrooms, but not the values). BCV, BWV and VWL did not make their rooms large enough to fit the sleeper chair in and do not look like they are likely to get the sleeper chair during renovations (BWV just got renovated with no sleeper chair). I can't remember if SSR is getting the sleeper chair or not.
Note that MOST DVC studios are a Queen bed and a full pullout. OKW has two queens. The DVC pullouts are pretty comfy - but not everyone likes them.
If you want to sleep five, your studio options are most, but not all Deluxe resort studios or POR with a trundle bed room.
DVC rentals can be a great deal - but you need to value the difference - and its a subjective value. Daily housekeeping - for some people its a big deal, for others it isn't (it can be purchased). Ability to rebook and get "
free dining" if its announced and is a better deal - not available. Private transaction which does carry some (not a lot, IMHO) risk. For me, a big one, much more onerous cancellations policies and much less flexibility once the vacation is booked - its much harder to add a night or move a week with a rental. Also, I've been a member for years, and while I think its a good value, I'm one that believes the customer service is not there for members (or their guests and renters) like it is for cash guests.