Re: Absorbtion and Duplication?
Dramatically speaking, the 'half goblins' would be smaller and weaker. Each iteration would be about 3/4 Body and Stun of the previous goblin. So a 150pt Goblin would summon 2 120 point goblins (19pts). The 120pt goblins would summon 90pt goblins, 90->60, so on and so forth. It would be infinite if the 150pt Goblin summoned another two 150pt goblins, and they in turn summoned another two 150pt Goblins, etc.
If I used duplication, I would start at a 150pt goblin, then 125p goblins, then 75pt, etc. Keeping in mind that each iteration after the first pays 2 forms of duplication - cost of its creator, and it's own duplication power. So the first goblin has 120 points to spend, the second 70 points, then 40pts, then 20pts on things like characteristics and claws. And they all share damage, too.
So I looked over Summon again last night, and it seems to me to take an extraordinarily long time to execute. Full phase to use, and then a full phase to recover (in which the goblin cannot take any damage, as per the Stunned Rules). I didn't see anything to speed up the recovery process as part of summon, so all the PCs have to do is deal 1 point of stun to the goblins as they're Stunned and Recovering, and then the monster's cool-ness is moot.
Using trigger would mean the goblins appear instantly in the phase it's killed, and spend the next phase recovering. Which doesn't really speed it up any. I could buy each of them +1 SPD (only for recovering from being Summoned, 1 charge, Never Recovers) and rule that the pt of speed occurs between the current phase and their next phase.
So if they got summoned on phase 4 (SPD 3), and they would go again on phase 8, the +1 SPD allows them to recover on phase 6. But that seems to me to be a GM call just to make my monster work. I.e. "because I said so" instead of following the base or optional rules on p 357 of the 5th Ed. Rev. Rulebook.