Jebus Cross

In that case, players who have lost their chances after 3-4 rounds simply give up... and then there are technical issues... which isn't good.

If you make a group stage, after three rounds, half of the players won't be playing anyway, but at least people will be interested, and they give out ratings for some places....
However, I would make it simpler: put those who give up on the tournament on a blacklist and don't include them in the next one!!!
And there will be 6 or 7 rounds. It won't be that difficult to play!