I don’t think the OP has said that his suggestions are needed, desperately or otherwise. He’s just playing with ideas that he’d like.
To the idea in general, I and others see it as generally ‘out of scope’ for future patches and would prefer new commanders and maps. But that doesn’t mean I haven’t thought about it sometimes, so I can play along. Note in the below that I’m unapologetically looking at ideas for new variant unit types, not just adding unused versus/campaign unit types.
Raynor: The manual cast ‘Snipe’ part of a Ghost’s kit would fit reasonably well, increasing Raynor’s infantry diversity. But EMP and nukes don’t fit into his playstyle for me. Something I think might be fun and fit a bit better would be Dropships. Not Hercules-spec (normal capacity, no teleport) but decently fast. Key bit that could make it interesting would be some kind of survivability buff (temp shield) to recently dropped units. Would open up a playstyle of doom drops and paying a ‘Dropship tax’ to improve your unit retention. Tankivac never ever going to be Swann level, which is for the best.
Kerrigan: Thing with Kerrigan is her army has a certain vision to it – the fierce, aggressive and vast sides of the Swarm. Infestors, Roaches, Corruptors, Swarm Hosts… just don’t fit that vision, for me. If she got a new unit, a Devourer variant would be nice. Shoring up her anti-air would help P0 vs P2/P3, and the variant could be given some minor spellcasting (say the unused Leviathan Bio-Stasis to make it a disabler).
Artanis: nah, adding anything would take away.
Swann: the Liberator suggestion in the thread is actually kinda’ interesting.
Zagara: Hydralisks and Infested Terran access would be counter to her gameplay vision of severely limiting her access to units that can hit both ground and air. I’d be up for a spellcaster though. Probably a bespoke Infestor designed to play a support role (not a summoner). Microbial Shroud’s name/look could be reused for a ‘lifesteal aura’… it’s a shame, Fungal Growth and Spawn Broodling would both be interesting in her kit, but that’s stealing too much from Stukov.
Vorazun: difficult. The most interesting angle for a new unit for her would be a ‘tempo increaser’, something that can help her make the best of early Centurions and Stalkers. I’m not sure what that is. A Nerazim Sentry feels weird, but the fact that Sentries are classically a low tech spellcaster ‘bandaid’ fixing early game issues does suggest it might fit. And I’m imagining that the actual abilities could be totally bespoke. So hey, maybe. Use the old Nullifier name and give it unique abilities and it could be a goer. Fitting that name and helping early game tempo would mean stuff like single-target disables (include structures: problem is it steps on Void Stasis), or high micro ways to reduce damage taken (maybe a single target manual cast damage reduction?)
Karax: Strongly feel that a solid all-round Stalker variant would mess with Karax’s gameplay. An anti-biological, focused anti-air ground unit would be much more okay though. So… heavily variant-up the Stalker model into something new?
Abathur: yep, no need.
Alarak: Alarak… ugh. Design-wise I struggle with him a lot. Blood Hunters’ design space has been used by Vorazun’s Dark Templar. And honestly, Tal’darim units are generally a mess. Copy-pasted existing units with variant mechanics, but most (outside Alarak/Ascendant/Supplicant) don’t fit into a cohesive fantasy. He is most in ‘need’ of more units, potentially plural, but… ugh. It’s a bigger task.
Nova: I don’t really like the idea of Medics for her. She’s kind of perfect as-is. If anything, look at sharpening the role of her Marauders and the age-old problem that Hellions are worthless.
More maybe later.