A bit of a rez but this thread was the closest to what I was thinking about for updating trees.
Tree Age & Type
I like the idea of tracking wood based on type of tree. I don't like the tree outputs (1 big log, X little logs etc.) as I think wood should just be tracked as wood. Once a gravel system is implemented for rocks, we can start tracking branches vs. trunk etc. but for now let's try and at least keep the UI simple. Wood is wood. As for tree profiles, having "this type of wood produces X logs" is one thing, but I think tracking "light levels" for growing rates is crossing the line into ridiculous-ville.
Tree Size:
I was thinking that saplings should be saplings, regular trees should be regular trees. However, especially in elven forests there should be a new terrain that is basically a "gargantuan tree". This would be represented by having "minable trees". Basically a mini mountain with vertical sides and outgrowths. The eventual goal would be to enable elves to build their homes on top of these trees (in the similar way that you can build on top of mountains now) or carve out the insides of the tree.
So maybe a tree might be 20 z-levels of a 10x10 trunk with branches extending near the top. You can build stairs inside or outside of the trunk and then build platforms etc. on top of the branches.
I think at a basic level you don't need to worry about killing the tree, but you could have a "core" that if dug into would "kill" the tree. It would have no impact on the tree in the game (no rotting or stuff falling off) but elves would consider this a HUGELy punishable offence, and would declare war immediately. If playing as elves, it should be treated as impassable "The elven miner refuses to breach the heartwood of this magnificant tree".
Anyway, you would mine it like rock, except using axes instead of picks and each square would drop wood instead of stone.
3Ripping trees with strength
Interesting concept, wouldn't be opposed to it at all. In the far future when you can have multiple races in an embark, having a giant "tree cutter' might be highly effecitve.
Fallen trees:
Once the tree is out, the wood cutter should just queue up a job item of "chop up fallen tree". Whether by axe or by hand, the "fallen tree" object is converted into X wood objects (X depending on tree type & age). As shared labor isn't implemented nor does it look to be done anytime soon, it's hard to predict how you'd have teams of dwarves haul back trees, so why not just have it done on the spot. That's how it used to work, they'd saw up the tree where it lay. Now they have cranes that can load up the timber into trucks, but back then with a full-sized tree you'd need a crap ton of dwarves just to move it...why even bother when you can chop it up on the ground and haul "dwarf-sized" pieces of wood back at your leisure?
Outputs:
Tracking planks vs. rounds seems trivially micro. I like how you can have rough wood and smooth wood. So the rough cut wood is hauled to whatever wood stockpile you have. You can either use it as is in a carpenter shop or you can bring it to a sawmill shop (or maybe even carpenter shop does both, think of the jeweler cutting AND encrusting in the same shop). There you can have wood smoothed. It will result in nicer outputs from carpenter, craft, and bowyer shops (wood burners don't care), but at the added expense of time.
Workshop profiles could be set up to say "only use rough/smooth wood".
The system proposed above is nicely thought of, but seems horrendously complicated as a whole. It can be hard enough to track stuff for the more complicated mechanisms as is, but adding this kind of micromanagement to simple stuff like beds and barrels is horribly tedious. I don't want to have to keep track of 5 different stockpile items to create a simple bed or barrel. Keeping it to smooth/rough wood is deep enough without crossing the tedium threshold.
I think a better solution would be to just increase the log requirements as appropriate and assume the "carving" is done on site. So if you build a barrel out of "rounds" then you just get a single smooth plank, call it retroactively "a round" and go from there. Instead of needing a beam, it just takes 3 planks that are retroactively considered "part" of each other.
Even if planks vs. beams vs. rounds are tracked, you definitely should never track halfsies as that just gets into tedium. Notice how you don't track "half" stones or "half" bars. It's assumed that anything not used in construction can be used to help "assist" other constructions or just disappeared as waste.
Waste/Byproducts
On that note, please oh god no sawdust. Please don't make my dwarves haul around one unit of saw dust every time I want to make a bed, or worse yet use up valuable storage devices like bins/barrels/bags for sawdust.
I actually like how tedious stuff isn't tracked, like biowaste and waste byproducts from reactions (like gravel, smoke, sawdust). Sure it's not quite as realistic, but neither is the abstracted system of eating, sleeping, and drinking. Right now critters eat what, twice a year? Abstraction is NECESSARY to make the game playable.
For those of you "realism is king", just realize that the "scrap" is saved to help fill in gaps later. So when a dwarf accidentally screws up a joint, he can get some scrap wood from a bin. At least in all my carpentry projects, I always need scrap wood here or a bit of sawdust there. Actually tracking it in a game would be tedious, as it's usually used for ad hoc reasons (oh, the chair is a little wobbly, here tack this on the bottom to even it out). Again, a level of abstraction is necessary to keep the game from collapsing under it's own weight.
I am comfortable with sawmills generating "maisma" during the smoothing process. Dwarves don't like sawdust flying in the air so I do like the idea of "encouraging" some kind of ventalation system. Maybe it could be done with forges & wood burners too, but I believe that dwarves don't mind smoke at all which is why it's not tracked as "maisma".
Tower Caps
Should be treated like any other tree, except they have the [UNDERGROUND] tag on them (or whatever) so they go underground instead of on land. Otherwise, they should be identical to trees. Just like you dont' eat saplings, you don't eat small tower caps.
FruitTrees
This would be neat. Have "some" regular trees produce fruit. They'd be restricted to appropriate climates (apples = temperate, oranges & bananas = tropical etc.).They should be visually distinguishable so that players wouldn't accidentally cut them down, but you should be able to cut them down.
Perhaps when designating trees to cut you can select "All trees" (default) or "Non-fruit Trees" to avoid accidentally cutting down your apple orchid.