Romo can't stay healthy if he actually sees to field, so not him. I'm cool with him retiring with full range of motion and able to walk and strong mental facilities.
Witten's 2017 production was easily replaced by our trash heap of 2018 TEs, so not him either. Unless he secretly spent the year off taking illegal performance-enhancing treatments to restore his athleticism and turn the clock back 5+ years.
Have to go with Ware, I guess. His ego would have to accept a bench role and bench-player money (which I imagine he couldn't handle, but this is a hypothetical), but he could thrive as a heat-seeking missile who plays limited snaps in obvious passing situations. Wouldn't have to keep himself bulked up to handle the running game or handle the workload of a 3-down player. Just whittle his body and technique to the point where it's built for quickness and pass-rushing and nothing else. As a role player off the bench, he could've extended his career by years and probably tacked another 5-ish sacks per year onto his career stats while he enjoyed the specialist role with less wear and tear. But I'm sure he's enjoying his retirement and coming back for bench-player money wouldn't be worth the injury risk and the working out.