For crowds (not corporate), Friday to Monday would be best.
The current Sunday to Wednesday was not popular with the commercial department, as day one was always one of the better days for selling corporate hospitality and that will not happen on a Sunday.
Would there though?
This proposal is suggesting adding 15 extra overs to each day, so in reality compared with a test in its current format, we would only be losing 30 overs, so one session.
How many games do go to a fifth day and how many go to the last session on the fifth day?