Narratively, I don't think it's likely that we'll see Unmade fabrials. The superweapon role seems to be occupied by the Dawnshards right now.
Also, the Unmade interactions that we've seen so far: Shallan realized that Re-Shephir was trying to understand humanity and creating twisted parodies, Nergaoul acting like a pleased hound when Dalinar let himself feel the Thrill, Sja-Anat wanting to defect, Yelig-Nar needing to be controlled and Ashertmarn's careless hedonism. They seem to be playing the role of subverters, who I think might end up getting subverted themselves. "They were once made, then Unmade", perhaps they could be Remade? I think that the Unmade were once something else who were Corrupted by Odium, but they can be turned back. The overall themes of Stormlight: unity, redemption, fight against hatred, makes me think that this is what will happen with the Unmade.
But that doesn't preclude the Unmade from getting subverted and weaponized in the form of fabrials during their story arc. It would be interesting. It'd also be interesting if they get Bonded... but the way Brandon reacted to the question of whether or not someone could Bond an Unmade made me think that one could technically do that but it's not something that we're gonna see happen.
Fabrials seem to require specific types of gemstones. We haven't seen a perfect gemstone used as a fabrial. Would different coloured gemstones be able to produce different kinds of effects from the Unmade or would only specific types of gemstones work with specific Unmade? I think it would be the latter.
Nergaoul used as a Rioter fabrial sounds quite reasonable. Perhaps Moelach could act as an Atium fabrial. Most interesting would be Yelig-Nar, who might become a full Surgebinding fabrial with all Surges.