Honestly, it's a good idea with a few loopholes NASCAR is refusing to close. It's mainly in to prevent say, Matt di Benedetto missing the race if he crashes in quali and then runs bad in the Duels. That would be bad as he's a driver who has the potential to win the race. That is absolutely understandable.
Unfortunately, the current system allows Ryan Preece (who despite his bad year last year, ended up 30th) to be without one while a RWR car 40th in points can.
A simple tweak to fix it would be to give charters to the top 36 cars in points, and then any withdrawing teams can be replaced by new ones or those interested in buying a charter from the open teams.
With that said, this would likely still end up with RWR having at least three charters due to the teams closing down at the end of last year. However, the #96 team would have a charter as they were 31st last year with Suarez, as would the three new entries (#95, #13 close down and #00 would lose the charter). The question would then be if Timmy Hill got enough points for the 66 team to pass a RWR car. (I'm not sure on this as I can't find reliable owner points anywhere).