LABOR-Develop a reasonable labor requirement to cut cost the Govt, would otherwise spend on Fed employees, contractors, or private sector. Since they are receiving better healthcare than most, cable which some still can't afford, and exercise equipment which some can't afford or are to busy working to use, we might as well educate them and give them a skill so they may positively contribute to society. Maybe in the process they will learn the error in their ways as well (we can only hope).
GREEN-Solar Panels, Recycling, energy generating exercise equipment, green rooftops, etc. (zero or near zero out as many costs as possible). All Fed facilities should be green, even if the cost is hundreds of billions of dollars to outfit all facilities, the savings would outweigh the cost. And with a skilled and educated labor force in the prisons they could install them. The Govt. will have made such a dedication to green energy that it would push new and better innovations in the field, as well as set an example for everyone else.
MILITARY SERVICE-Allow certain individual to serve their country in a support position. Even though military personnel are not the highest paid individuals, BOP inmates are paid even less for their work. Savings in military contract workers as well.
FOOD-Feed them Nutraloaf. it has all the nutrients a person needs to survive, and is a lot more cost effective. It is already used for additional punishment for prisoner but can used across the board. People say ti will cause riots, but that will cause lockdowns, and they will eat it when they get hungry. Prison is not a scholarship.
INTER-CONNECTIVITY-Why couldn't certain Prisons cultivate there own food and zero out that cost as well. Remote larger Prison facilities would be centralized hubs/distribution centers for the rest of the system, while Prisons within a more populated area, can focus on tasks such as maintenance of facilities or upkeep of public areas.