^A BPRD spin-off would work very well though IMO, new characters like Roger (a favourite of mine in the comics), Lobster Johnson and Kate Corrigan could be introduced, and the likes of Abe and Johann could take centre-stage while Hellboy is away.
It could introduce us to more elements from the Hellboy/BPRD world and create a bit more awareness for when the 3rd movie comes out, meaning more success for it.