Horses for courses.
The solution is to choose the airframe for the job, not to just pick up whatever is around and make it do 3 separate jobs.
For the Iraq, Afghanistan run a large twin like the A300 would be adequate: there are freighter and passenger around.
For MPA, go for the 747-400: lots of capacity and 4 donks for long overwater legs, freight capacity and freighters also available.
Convert the T*s to tankers and let them concentrate on that.
6 A300s and 4 747s would cost around $300 mill on the secondhand market.