How about swinging some healthy tissue into the area, muscle or fascia flap?
I've started doing Rectus Myocutaneous flap closure of perineum after
perineal resections and I LOVE IT! It only takes an extra half hour, you
get vascularized skin pedicle, and the bulk of the muscle occupies the huge
cavity created in the pelvis. Especially useful in already radiated
perineum, where skin and tissue is suspect to begin with. Your fellow may
need tensor fascia lata, gracilis, or gluteus.