Terrible idea. I don't see why this would cause more teams to try to win more. This proposal allows you to be even worse and still have a shot at the playoffs. The proposal incentivizes teams to finish 9th or 10th over 7th or 8th. This year Charlotte with a 30-41 record so far would be in position to make the playoffs and have a chance to get a top lottery pick. Why would we want to reward that? In the West, Denver and LAC are still trying to win to make the playoffs. Under this proposal, they would coast to a 9th and 10th finish.
Also it isn't just one extra day. The 7th seed hosts the 8th seed while 9th seed hosts the 10th seed. Then the loser of the 1st game hosts the winner of the 2nd game. So it would be 2 game days and 2 travel days at a minimum.