It would take a lot of work which I think given the current state Disney is trying to avoid. Much smaller more spread out waves of people. Spectators restricted from runner areas. The list goes on. It can be done though. Space coast is going to do it.
The issue is going to be the regular bottlenecks that are impossible to maintain any degree of social distancing - path from DHS to Boardwalk, backstage areas in Epcot, finish line, etc. I think runDisney will wait until the new year to decide if the races will be on property or switch to virtual. See how the numbers are once flu season commences and the holiday season is over.