just throwing a random idea in here (without 100% reading every word in here.. tired.. and just want to throw the idea in here):
what if elves dont build/construct/craft anything but instead grow everything. (well no idea "how" to mod it or if it is possible.. and also didnt really read every linked topic in here... but i guess the basic idea of "growing" is with elves anyways)
lets say they have some sort of seed/growth building that you "construct" that kind of works like the warlock pylon... just in like 10 tiles around it on the same z level it slowly auto constructs constructions from the closest to the furthest.
and to grow a z level above you have to "expand/grow" the "growth stem" whatever building with some reaction on it that grows it up one tile (i.e. on the pylon you select "grow z level up" and if you placed the same construction ontop of it it grows it then. and then can grow constructions on 2 z levels. 2 pylons ontop of eachother each with a 10 (? random example number) field radius to grow around on the same z level!)
these grow seed stem buildings thingys would be pretty valuable to keep... similar to how warlocks are pretty valuable well for the warlock race. so if invaders destroy them it would be pretty bad (as they might count as building? or might even be a stationed creature that can be killed... no idea... either way it would be "problematic" if i.e. one bit disappears and everything floats in the air. so not ideal.)
maybe normal growth of walls/stairs/constructions would be .. normal speed. (2 game weeks? no idea .. some timeframe)
the growth z levels up would take a bit longer. (i.e. 3-4 weeks)
and maybe you could build special branch floors that are relatively quick to grow (1 week?) but need to be connected to the stem and that extend the grow range by 1. (basically range 10 around the stem and each branch floor)
maybe the longer the "age" of the stem/trunk/grow building thingy the more branches you can add to that z level... so the lowest parts can have the longest branches and the very top one just a few. (+ 2-5 branches every season?)
maybe the (floor tile) branches would over time grow into trunks (walls) same as the starter grow thingy... so you could have big trees over time and could build rooms inside them. (well with some way to remove the walls again... smoothing job? that makes them into trunk floors then?)
maybe they have some sort of "mother tree" "building" that is the main "base/foundation" of the fort and works the same as the grow "saplings" described above... but the branches of that tree can create new saplings and the trunk bits can "spawn/generate" normal wood blocks that are then used to be placed as constructions and then grown.
another idea is some sort of "fairy" creature that tends to these grow trees... and they are who actually construct the wood then. (as the whole based on time mechanics might be way too much.) maybe these fairys are somehow assigned to the mother tree/growth saplings and then move around it to move wood from the trunk to build the branches or so.
maybe the mother tree could have another function to create fairies? kind of like hives and bees? (very abstract comparison. maybe how skeletons are used for warlocks for "everything"... fairies are used for elves to "build their trees"/builders. (pretty much totally useless in combat though unlike skeletons, maybe can be trained into combat wisps or so))
maybe a fairy "working" in the trees/branches/workshops makes parts of the tree grow faster?
no idea how the timed everything would actually work... well the warlocks have some timed stuff like the blocks that disappear or the summoned weapons. no idea if in some way such a timer could be added to i.e. a wall block or a floor tile and after X seasons the floor(branch) changes to a wall tile (if nothing is standing on it or build on it).
(also planted plants somehow have a timer that changes them/creates the end plant after a while, who knows if something from that helps)
maybe it would be very abstract possible with 3 different materials... young trunk, trunk, and old trunk (or something similar) and lets say after one year it changed from young to normal and after another from normal to old? so the very first build trunk "walls" end up as the oldest and inner most while the outer "bark" is the young trunk? and maybe the young and normal trunk (walls) can be shaped back to floors and doors to build rooms? where the old trunks/walls/floors are considered higher quality "smoothed" (compared to stone walls)
and maybe you have special workshops for i.e. wood generation, fairy generation, item generation that you can place on the branches (floor tiles)
maybe the starting wagon could be converted into the mother tree? that grows faster the first year ? or just faster in general? and the growth saplings you can "build" wherever you want grow slower ... so the mother tree is always the biggest tree? (so you actually can build i.e. workshops on branches etc... and are not stuck doing nothing till the tree grows)
the whole "killing/destroying" of trunks etc is a awful idea actually... so the trunks are just walls basically and cant be destroyed. the workshops in the branches could be destroyed though.
if the tree trunk is considered "walls/range pylons", and the branches you "build" onto it are considered "floors" maybe you can build "leaves" on the branches that are considered "fortifications"? (elves in the trees shooting arrows without penalty... etc)
maybe you can build a 3x3 "sapling trunk workshop" that is the base for new "fortress trees", and cost special "seed blocks".
they might look like this:
WFW
FXF
WFW
(W=wall, F= floor, X = up down stairway, well whatever works... but i.e. that way elves could walk around in trunks and move up and down the tree.)
and next to these you can build "3x3 branches workshops(?)" maybe similar to how you build addons to the human guild buildings? and maybe you can build 3 3x3 branches far out to a trunk. i.e.
---BBB---
---BBB---
---BBB---
BBBWFWBBB
BBBFXFBBB
BBBWFWBBB
---BBB---
---BBB---
---BBB---
(well this is just one attachment... you could build 2 more branches to it everywhere for a 30x30 block of tree. maybe branches can be 9 tiles away so you can build 3 3x3 onto trunks.)
maybe instead of timed auto growth of branches into trunks there instead could just be a reaction that turns the branch 3x3 workshop into a trunk workshop? (so you then can build new branches further out?)
maybe the mother tree would instead be 5x5 with 5x5 branches? as special tree... and you can run reactions on the trunks to create branches (to build branch floors) and seedblocks (to build new trunk workshops?)
well the other idea is the "pylon/creeptumor" idea that you plant/build the "grow trunk" (workshop?) that ages over time and allows construction X tiles away from it. the older the further away. build branches need to be connected to it. and branches turn into wood/trunk over time that way the tree trunk grows outwards.... and you add branches to it over and over. (awful idea) and the pylon has a reaction to "grow upwards"... well or the pylon doubles as up/down stairwell and you just build a new young one ontop. and the walls the branches change into can be designated like stone so you can dig out stairs and walls and floors etc.
maybe branches first change into leaves (fortification) and then into trunks (walls)? and then age with old trunks = smoothed.
i guess all this is way too "hard-coded mechanics" and would be way better done with just a "mother tree workshop" that spawns wood logs... and then you just build your own trunks (walls) and branches (floors) and stairs etc... and not all this workshop etc over-complication nonsense. and the restriction about "you can just build so and so far away from the trunk with different ranges based on how old the trunk is" would make sense based on a tree... but is probably also irrelevant as game play element and too restrictive.
oh well i just thought maybe something that grows over time in some way would be neat, with distance based on age.... well was just an idea anyways... who knows maybe some bits give other people ideas how to make something way easier and better