Well, I can take a crack at it. I’m going to throw three “feathers” into the air, and then combined the concepts.
Feather 1: Technology
I have unpopular opinions as far as Night Elves are concerned having to do with their relationship with technology. This character is one that I RPed as a warden, recalling that in Warcraft III, Tyrande found that Wardens were hoarding goblin land mines. She even has a voiced line about it, and generally it’s a good idea to use them.
This isn’t an isolated incident. Night Elves do not display any outward issues to technology as a concept - just when it should clash either directly with them, or with their established values - and this can lead to wonderful situations like their odd partnership with Gnomes at Stardust Spire and in the Stonetalon Mountains. I do think this has to have limits of course - I do not expect to see Night Elves developing and using gasoline engines or being comfortable with weapons that interfere with their style of war. That wouldn’t preclude explosive-tipped arrows though, or living constructs that take advantage of mechanical principles rather than being powered by the arcane or by gasoline.
Feather 2: Organic Construction
At the same time, I think that wisp-driven and druid-driven construction has been vastly underutilized. In Warcraft 3, you could grow buildings with wisps that were able to manipulate stone to get us there - wisps also harvested gold, a metal, and if we extend moving and shaping of parts that would be required for them to be able to repair glaive throwers and ships - some metals likely would be counted as things that they can manipulate. The possibilities on offer I would argue are akin to what Avatar: The Last Airbender did with Earthbending.
Feather 3: Cities on top of cities
Deus Ex: Human Revolution has a fascinating little city concept called “Hengsha Island” - which is a city that in the game’s lore undergoes massive economic growth and population influx. Their solution for this is to have a bright, glittering upper city separated from the lower one by the “Pangu”, which is a large, table-like platform that the upper city sits on. The lower one, with this canopy, is often dark, packed with activity and complex - and the game does a spectacular job at selling the verticality of this city concept.
“Catching” these feathers then, the Teldrassil of my dreams is a highly vertical concept, with druids having grown chambers and passageways to link different areas together. The trunk wouldn’t be so much solid as it would be porous and open, with different settlements existing on different levels, as well as large parks and areas that were deliberately set aside to host wildlife populations. Many of these areas would be linked by something of a copy of the Deeprun Tram - only the tramway itself rides on deliberately grown and shaped branches, being thrown down the track by a series of animated roots. Necessary elements of the new Teldrassil would include things like a port, a rebuilt religious center around where the old Temple of the Moon was, as well as several villages. It would feel at the same time relatively open, but labyrinthine to navigate and consider.
Obviously, I am not a fan of the Night Elves being in a perpetual state of decline, and I feel that a shift in their ideology would be required to accomplish some of this. Someone would have to stand up and say “no, we’re not going to keep feeling sorry for ourselves and we’re going to stop holding ourselves back out of a fear of arrogance”. The new ideology would have to be against the sort of complacency and restraint that it would allege led to Teldrassil’s burning in the first place. While there of course would be dissent asking if this is abusing nature rather than serving it, they would be a minority in comparison to those arguing that in a world where the Alliance won’t fight for them and the Horde wants them all dead, they must now use every advantage they can, worry about arrogance and pride another day, and far more aggressively pursue growth and societal advancement.