I don't like this system. To play this properly I would need to be awake full 48h.
If sequential system suggested takes too long. Then we coukd have all leaders and nations under bidding simulatenously. One could have winning bid for only 1 nation and 1 civ (or 2 traits). We could state that auction is open at minimum 5 and at max 7 days and after 5 days you would at random time close the auction. If there are players without a leader/nation at that point they get randomly assigned.
If sequential system suggested takes too long. Then we coukd have all leaders and nations under bidding simulatenously. One could have winning bid for only 1 nation and 1 civ (or 2 traits). We could state that auction is open at minimum 5 and at max 7 days and after 5 days you would at random time close the auction. If there are players without a leader/nation at that point they get randomly assigned.

. To minimize fees cents instead of dollars could be used. Nevertheless auction system isn't worth it, if it isn't free of charge.