If you have no working relationship with the other airline CEO, then I think it's fine to do such shenanigans. If the plane you're pumping and dumping isn't a very popular one and you can easily replace in the used market, then go for dumping it. Keep in mind that more popular models are difficult to replace especially at the 8 year mark for the type.
However, when I'm leasing to/from folks that I have a working relationship with (i.e. within my alliance or an in-game "friend") then I'll typically return planes with a decent amount of D check left, or if they're destined to be scrapped, i'll send them a message with a heads up so they don't get auto d-checked by the system. I expect the same in return when I'm leasing to folks I know. As for the open market, I expect to get hosed :-).