Thats my thought. Overtaking must be a wide birth , and decisive like in cycling time trials.
That way can social distance the start in 2m intervals, 10 seconds apart. In half an hour can get 180 over the line. Easier for marshalls too!
I dont know if anyone has noticed, but all mountain marathons do this.
We did the reverse on a club race, where handicaps were used to aim at all finishing together..







