I agree some urban reclamation would make sense, or rebuilding - primarily temples. If you look at Darnassus other than the initial Terrace the only building that is made of stone in the city is the Temple; the rest are lodges. I’d prefer this theme is continued.
I’m well aware nelf have a history of arcana, but that is history, and the fact some of SD have rejoined them does not change that, the SD are still outsiders to the culture and their inclusion is more a gesture of tolerance of them, as opposed to championing their ideals. So it seems to me it’s more a case of “you’re welcome back, but you do things our way, okay?”.
This isn’t to say they’re required to give up arcana entirely, clearly that isn’t the case, but the days of nelf building dedicated arcane libraries and stuff are clearly behind them. I don’t think their culture has that element to it anymore - it should be pushed in the direction it has moved towards (druidism and elune worship) rather than pushed backwards.
We already have two elf subspecies (three if you count velf) that have the whole arcane ubrane elves, even if nelf “half-dip” into this, it’s oversaturation of a done theme, especially considering their lore has moved them away from it (making them more distinctive) so to push them back gently in that direction a bit makes them less distinctive at the cost of their USP (there are no other nature-based elves atm).
So yeah, reclaim ruins by all means if it’s plausible, but i’m not on board with nelf building urban structures outside of temples/places of worship because at that point you just begin to tread on the toes of Nightborne, even if a little.
People need to remember the SD are very much the outsiders in nelf society, they are the minority, and although tolerated that doesn’t mean they are championed. Tyrande didn’t exactly make it unknown what she thought of what the Nightborne represented so the idea accepting SD back in means nelf are perhaps more accepting of urban settlements isn’t there for me. Arcana is still something clearly viewed with distrust in their society and in my opinion they probably accepted the SD back on a “better the devil you know” principle than anything else.
Leave the marble buildings and spellweaving to the Nightborne and Belf and have the nelf create cities borne of the land itself. A huge conclave of buildings and platforms between great trees and beneath their raised roots for example. There is too much focus in game on what the nelf were (endless ruins and ghosts of mages) perhaps it is time to focus on what they actually are.