This post tells you all you want to know
When it comes to contracts mode and the server accepting things, they’re basically different systems. One is called contractconditions and the other is called gamechangers. Contractconditions is a very small specific list that we’re all familiar with and gamechangers are all complications in the whole game (there’s some overlap, and contractcondition IDs work as gamechangers, but not the other way around).
Sadly we’ll never get anything as a complication in published contracts that IO doesn’t put on the contractconditions list 
And even if we did, a lot of gamechangers (maybe half) are fake, they just exist to show a card on the briefing screen, and the actual objective for it is done manually in the contract’s script