My opinion on all of them:
**Averdian: **The alien thematic kinda clashes with the rest of the game,but having someone with psi-powers is actually something that is still missing in the game and while I think that such an alien looking guy would stand out I do think that a targonian aspect from a different planet could be fitting for the game,though they'd need to look more fantasy-like for it to work(just look at some of Zoes original concept arts where she looked more like an Imp).
**Gavid:**Honestly I don't see a future for this guy,Zyra got already the whole plant-mage thematic down(and its even focused on plants with thorns like gavid) and Maokai/Ivern are both walking plant persons already.So if they would make Gavid,then they'd need to completely redo him with different plants and a different body shape to differentiate him from the others.
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Tabu:**A voodoo-themed mage would be really cool and I think that there is a lot of potential there,though riot would need to be careful to not offend anyone with stereotypes.
**Eagle Rider:**If he was remade he would likely be a demacian raptor knight instead(assuming that he literally rides on the eagle) and would likely not even remotely resemble the original design.Though having 2 demacian bird champs would be kind of odd,so I doubt that he'd have a good chance.
**Avasha:**Was pretty much turned into Riven and I don't think she has anything going for her that makes her stand out.If anything they might just reuse her name for an unrelated champ
**Omen:**Looks really cool,but he'd need something to make him stand out thematically as we already have already some monster champs and Omen doesn't really bring that much to the table in terms of themes.So I'd really love a version of him,even if the only thing they keep is the smile and the fact that he is 4-legged.
Rob Blackblade:We don't really have a dedicated master thief or brigand,so Riot could do something with his theme,but otherwise there is literally nothing worth keeping about him.
**Well:**This is the one I voted for because I'd really like a water elemental.Sure we already have a water mage with Nami,but a water elemental still feels different enough to fit in and we already have elemental champs for the other elements with
even if they aren't literal elementals.