They don't have to waive Odom and pay him 2.4M,they can wait till he becomes fully guaranteed and trade his expiring contract.
I think Haywood could get traded with Odom to the Kings,that makes sense. Or Haywood is dealt somewhere else as he only makes 3/27, his 4th year is non guaranteed.
The ideal for Dallas is a three-way trade before the last year becomes fully guaranteed. The Mavericks send Odom to a team with cap space and get a future second-round pick plus a trade exception. That team sends Odom to a third team for salary it wants to shed. That third team then waives Odom, either to reduce the luxury tax bill or to gain some cap space (or to get under the luxury tax threshold so they can use the full MLE rather than the mini-MLE for tax paying teams).
I'm not 100% sure they get a trade exception, but I think that's how it works, since the year for purposes of the salary cap begins July 1. The trade exception does count against the cap, so they would have to renounce it in order to sign a big free agent, but it could be part of a plan B of keeping Marion and Heywood, maybe bringing back Jason Terry on a short contract (Jason Kidd, too, I suppose), giving more minutes to their youngsters like Mahinmi and Beaubois, and using the exception to bring in someone with an $8 million salary.