The elves never asked me to limit my woodcutting in my games.. (and i was razing a forest right in their face.. got ~650 logs) what triggers it?
As for siege.. i agree that elves should bring animals "buddies" to fight by their side.
Early its just some cannon fodder, later its giant eagles harassing your surface operations.
They could get the help of special monsters like mudman and stuff like that.
My view on elves: I like my ennemies smart!
Elves are master of the natural word eh? They are physically and technologically weak.. a direct attack is foolish against a fortified, trapped, heavily defended fortress. So they got to use their arts to their advantage. I see them as experts for indirect battle; attack the supplies, attack their morale. Use poison, use diseases liberally. Some call them cowards, i call them smart.
Elves could use vermin as carriers for nasty stuff to attack your fortress from within..
-A vermin that carry a mushroom spore that "freeze" crops tiles "infected" by it for a season, reducing your food production. Try to infest fields being used.
-A vermin (worm of some kind) that search and eats logs and wooden furniture/wooden stuff in general. Can have interesting effects when you think about it..
-A vermin that eats cloth, thread, and clothing, even when worn. Might be popular to get rid of goblin stuff.
-Another one that can infiltrate your secured food supplies and make them rot inside the barrels.. alcool included. Ruining both food/drink and the barrel itself.. maybe make content poisonous to the poor dwarves that eat it, doesnt kill, but decrease happiness for a while.
-Some other that simply carry poison/disease and try to transmit it to a single dwarf before dying
-Some vermin that is poisonous to cats (basically a kamikaze vermin)... but that one might be a little too popular with the whole wide world.
-annoying birds that try to eat seeds inside your fortress, might go on crop tile to steal the growing seed.
.. so if you dont have enough cats/anti-vermin set up you gonna regret it. But its easy to do and limit the damage.
Also..
- Fire snake infiltration in the wine cellar.
- water source made dangerous by carps or made contaminated by poison/disease, so you gotta wait for it to go away or purge your water supply.
-They could "for the greater good", infect the nearby land that slows down the rate at wich trees/plants grows. Or increase it to ridiculous levels so trees are always in the way. Or even invasive and some useless plants start growing inside the fortress. (basically inserting themselves into the cracks of the floor/walls destroying engravings= unhappy dwarf)
-If we push it, they could "call" storms to create a surge of the river, or "call" for a heat wave to come and dry up all shallow water ponds and dry up plants and stuff.
-(that would be extremaly dangerous) have some elven saboteurs try to disable traps/floodgate that they find. They can swim.
-edits; adding some stuff-