Dave seems like a sort of Burn based Cinq like character, if I had to guess. More burn the more speed you have (or maybe he has a unique haste that changes skills?)

John strikes me as a Poise Tremor hybrid. A unique self tremor that can work as extra poise count, maybe.

From what we've seen, guns are generally poise, but jade gives me pure rupture more than poise rupture. Maybe even unique charge.

Rose would be like Kraust, I feel. There are some offensive capabilities, but she mostly is used for debuffs/buffs. G Outis and Kraust fusion, perhaps. For an actual keyword, a minor amount of bleed affliction could fit well.

For the alpha kids...

Jake is a keywordless 00 id poise, similar to the fullstop office characters. Infinite reload, spends a ton of ammo at once like Hong Lu. Skill 1/2 gives a small amount of self sinking, S3 consumes it all for buffs. Built for mirror dungeons.

Roxy's Sinking. Similar aggro mechanic as KoD Rodya's negative sanity form, with the 0.25 aggro and all that. Applies various debuffs that scale in intensity based off of the enemies sinking, can steal/create buffs for allies.

Dirk is... complicated. He feels like he could be most status archetypes. Wouldn't be surprised if he got some sort of guard gimmick where it swaps around skills for ones of different archetypes, with charge being the only constant. Hell to code, but what about Dirk wouldn't be?

And Jane is Rupture. Applies team healing on every attack, if she drops to negative sanity, attacks lose healing and apply heavy rupture potency, but little count.