It's a mercenary realm that acknowledges the realities of politics. If Darka took every contract that was offered to betray their current ally, whoever that may be, they would quickly end up ostracised and ganged up on, and for good reason. KK is smart enough to know that. And so are you. So you don't want a greedier Darkan king, you want a dumber one. But for the record, no one in the king's council was willing to consider your offer. Darka just isn't a realm willing to sell its friends short.
You want political realities?
Here's one: No one in the Northern Alliance will offer Darka a contract because they are already fighting for the Northern Alliance. The only people who would offer Darka a contract are in the Central Alliance and their contract would only be against members of the Northern Alliance. The Southern tri-fecta are too busy looking at each other crossways and trying to stab each other in the back more often than the Lurians than to offer a contract to Darka and Darka is too far away anyway to even make that worth it.
So, if you want to ever be a mercenary realm (again) you either have to:
1. End this war.
2. Change up what the current sides are (which coincidentally is being slowed down by Kostaja....)
3. Or take a contract with a realm from the central alliance.
If you don't want to take one of those three, then I really don't think you have any right to complain about the current state of events. It's not like you're going to win the war against the central alliance militarily at this point. Y'all took down our city walls from lvl 5 to lvl 2 in a matter of days and within 10 days they were back to level 5 again without even denting Coria's reserve funds. I also know this heavily hurt Hammarsett's ability to keep up a strong army. If Hammarsett loses their full army even once more they will likely have a large problem trying to rebuild it without cutting into their militia.
So, if you really want to find something new and not betray your allies, I'd suggest having Kostaja and Aldarion put their heads together. Plan a little fake skirmishing on your border with Talerium for just two weeks and the Hammarsett problem is over and done with.