Oh HO HO, since the adventurer has never been implemented, then it's all tabula rasa, and I say that the TRAPAVOID BUILDINGDESTROYER precedent is too well-established to ignore, and I like jumping to conclusions because it keeps me in shape.
Ho-ho-ho, Green Giant. Tabula Rasa sucked, and I completely agree about the pine cage thing. Totally lame. Of course, adventurers are by and large game-breakingly inconsistent. Ideally, the new Titans would be tasked with insane whimsy and incredible power, allowing a more canon megabeast class to fulfill the role of the adventurer, which is really just a high-density packet of metagaming that menaces with spikes of nothing to lose.
Actually, an adventurer that's generated with vanilla DF specs would be a pretty fair inclusion. Give him the [trAPAVOID] and [BUILDINGDESTROYER] tags to accommodate the vagaries of adventure mode, but limit him to the best manufactured goods present in the world that your fort inhabits and give him skills that don't exceed 22 or so in any category and he'd be a fierce competitor, but nothing a half-dozen elite marksdwarves couldn't eventually shoot in the neck. Heck, most of my adventurers get killed by lampreys before they even try to genocide any civilizations.
I'd certainly support the inclusion of what amounts to emergent megabeasts, very powerful characters that can arise after the world has been generated and still have an impact on the game world. I don't know if anyone here frequents GameDev.net, but there's a regular poster there who goes by the moniker "Wavinator", and he seems to be channeling a lot of DF principles into a more abstract sci-fi context. He wrote a bit about the generation and disposition of significant AI figures in a dynamic world a while back.