Narratively, that’d actually be quite fantastic.
Especially if you’re able to combine ‘light’ elements with nature. We’ve seen void & nature within the Emerald Nightmare, and arcane + nature with the ancient Kaldorei and Nightborn - Seeing more variants would be pretty cool.
Perhaps finding a seed of that ancient tree that the ‘Thas’dorah, Legacy of the Windrunners’ was crafted from, to replant - Infuse with a Bronze Dragonflight element to grow into a tall yet still relatively young holy white oak tree - That creates a new bastion & staging ground of druidism – Would be a good start.
… Personally I’d love events or super-dungeons / miniature raids that once completed the questline of actually transform the zone — Like ‘Strongholds’ in Diablo 4 (Then perhaps for gameplay purposes, have an NPC to go back to instance should you want to repeat experience or go back for loot). There’s so many areas & lore rich zones that’d be fantastic to turn into towns, small cities and hubs — Utilising that system to widen influence on the world and actually SEE it change to your actions would be awesome.
Personally I’d love priests to have a stronger role outside of being fodder for the story of Paladins as the ‘Lesser form before evolving’ or nameless healers who are STILL outshone by paladins, or simply slaughtered with ease.
Like, having some strong new characters come into the fold would be great – Even having Blood Elf priests join ‘The Blood Knights’ after showing their own merits not to be underestimated would be grand.
Personally I’d love it to develop into earning a spell-customisation for the race (Like ‘Light’ visage of shadowform and light visuals for the spells) – Though I feel that’d probably be in the ‘Less likely’ section, knowing small efforts with big results are usually overlooked by Blizzard.
A good story to develop would be to make Quel’Thalas an overall sanctuary for their kind, not having to choose between Alliance or Horde but simply embrace their traditions, culture & home (aside from those filthy void elves) and being marked with a powerful holy ‘pacifier’ spell if such is the case to detect & alert signs of hostility to their values, or a flare of sorts if an attempt to dispel it within their kingdom is made.
You could put that ingame - where you can speak to a neutral NPC to be ‘marked’ and become neutral or friendly to all NPCs within the zone. Have another NPC for Void Elves who can use a ‘dampening’ artifact to immensely draw out the void energies to prevent their influences, then apply the mark. Simply talk to them again to remove it, or exit the zones. These NPCs will be held outside the city to prevent infiltration into assaulting the leaders of Quel’Thalas. PVP would be disabled, except for within a particular arena – However duels would be allowed.
With the suggestion I made earlier about strongholds being earned, you could use the same principle of sorts (Being ‘marked’ and made neutral within borders) for newly formed towns & small cities throughout Azeroth.