In init\d_init.txt you can set new invasion force.
[INVASION_SOLDIER_CAP:120]
[INVASION_MONSTER_CAP:40]
Expect some measurable lag though on larger force arrival.
Being able to dispose larger quantities enemies can turn tide.
Just make sure there are no gobbos fleeing, as they get experience this way. No gobbos should survive the siege.
My solution is bridge at start. Then long and wide under ground hall to contain them all nicely. Then narrow cage/trap hall alike this:
xxxxxxx
++x+++x
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
xTxTxTx
x+++x++
xxoxxxo
x-wall
+-floor
T-trap (cages are very nice for goblinite, if your mass pit works ok)
o-quick access bridge for engineers and haulers to clear, clean and reset traps.
You can be viciously efficient in cleaning invasions and receiving huge pile of goblinite.
Keep your engineering "squad" with 10 mechanics. Normal or strong, never weak. For fast skilling engineers have to be both intelligent and creative. Intuition and memory alike medics should be additional bonus attributes, if you want them turned into scholars later on. There are few books they can write for your library.
If you find perfect engineer but weak, save him for medic.
Sometimes it pays off to ignore the skills and pay attention to the right attributes.
The only issue I find, that my Dwarves can be picking cloths up and wear it. Foreign clothing, that I do not desire in my fortress and which can not be produced locally. So sorting through goblinite can be tedious at times.