I think this will depend on how far the Pels end up going. If they make WCF, it's hard to argue signing Cousins would be helpful. Davis-Mirotec at the 5-4 was killer. I don't believe the same dynamic would happen with Cousins back as a starter, and he isn't coming off the bench.
Being stuck with a mostly useless player on a massive contract for years kind of sucks. $30 million a year is a lot of cash to pre-pay for finding out if the Boogie/Brow experiment is worth it, especially after you signed a hungry Mirotic and are getting benefits from that right now.
Well, it's been proven that they have a much better winning percentage when Cousins doesn't play. 2017/18 without Cousins 22-13 projected out to 52-30 and 3rd seed 2017/18 with Cousins 26-21 projected out to 45-37 and missed the playoffs (10th place) Pelicans also struggled last year as they were 13-11 with him. You may not like numbers but they have to at least be a big part of the decision making.
I think you'd have an easier time getting value out of Cousins than Vonleh... You could trade Cousins for a large expiring deal and draft pick, or any number of creative things. We've done that kind of thing plenty of times. Vonleh didn't have near the upside that a Cousins deal would have. You can't just let that go if you want to compete. *Edit* However, if he has really gained a ton of weight then I'd have to make the decision based on a physical assessment. If he's not willing to do a workout that says a lot.
Another factor is they also need to be able to sign Rondo in the off season and then the next year and Mirotic comes up for contract. It might make more sense to see if they can do a sign and trade with a team that has some cap space as well as some assets that won't bloat their team salary as much as Cousins would. Lakers could be a team in that category. Maybe an Ingram/ Kubac for Cousins and lakers absorb the difference in cap space. Or replace Ingram with Kuzma. Pelicans won;t have a huge luxury tax bill and a quality 3/4 player that could be an all star and a young prospect at center to back up Davis.
My Vonleh scenario was really only meant to demonstrate that teams value being under the luxury tax, not as a comparison of players. Re-signing Cousins makes it difficult when he becomes trade eligible and would be after the teams with cap space have likely used up majority if not all of it so that might not be available. Better to do it before the season in a sign and trade like I outlined in my other post.
