Yeah, the way rooms are booked, that wouldn't work well unless you knew the people and were comfortable adding them to your reservation (i.e. like booking a stay with friends and they reimburse you for part of the cost). They would have full access to your room.
If you booked it and rented one room intending to not even tell Disney that a different party was in the other room, that would break the rules and result in the renters not getting any of the perks of onsite stays. They wouldn't even be able to park at the resort, and you could get into some major trouble over it. IMO, not worth it at all. It sounds like an easy way to get permabanned/trespassed.