Sounds fair to me. As long as the work is done.
However, since it was the publisher who decides, and there's more writers who had raised interest, I'd like to ask you to create your version of the story with the characters I have, (a 1-2 page summary) that I can submit to the publisher and see their opinion.
Write me an e-mail to astralnight017@gmail.com and I'll send you the infos, if you're still interested