The drune lords, and their destruction of the earth to fuel their magics, could make an excellent Front, or at least a Threat.
I only ever read The Horned God series, and then some two- or three-issue run about Slaine and a drune lord fighting off Norsemen on an airship. Both were really awesome, full of blood and sex and really creative name-calling, and I think they're enough by themselves to demonstrate that the series can totally do Apocalypse World kind of stuff.
I think the psychic maelstrom could very well be the power of the earth. It's going to be more multi-faceted though, since earth-heroes can use it for warp spasms, but it's gotta be the source of divination for druids and witches and so forth.
Having a combat-monger archetype who incorporates Weird (or whatever you use for the equivalent) would be pretty exciting.
Kaiser, what do you think the comic's "holes" are, as far as building a good hack? They've been publishing the comic for 20+ years; you can do it!