1. Swap the goblins with dragons in the raws.
2. Wait for seige to come.
3. Prepare your fortress.
4. Profit??
If your champions are better than that, which they most likely are, copy this over the goblins in the raws:
[CREATURE:GOBLIN]
[NAME:avatar of armok:avatars of armok:avatar of armoks]
[TILE:'A'][COLOR:3:7:1]
[DRAGONFIREBREATH][MAGMA_VISION][FIREBREATH][FIREIMMUNE_SUPER][WEBBER][THICKWEB][WEBIMMUNE][PARALYZEIMMUNE][FLIER][AMPHIBIOUS][liKES_FIGHTING][FIREIMMUNE][EQUIPS]
[GENPOWER:5]
[SPEED:0]
[FANCIFUL]
[CANOPENDOORS]
[PREFSTRING:evil glory and majesty]
[BODY:HUMANOID:2EYES:2EARS:NOSE:HUMANOID_JOINTS:5FINGERS:5TOES]
[NOT_BUTCHERABLE]
[NOPAIN][EXTRAVISION][NOBREATHE][NOBLEED][NOSTUN][NONAUSEA][NOEMOTION]
[NOSTUCKINS][SEVERONBREAKS][NOSKULL][NOSKIN][NOBONES][NOMEAT][NOTHOUGHT]
[NOEXERT]
[BUILDINGDESTROYER:2]
[DAMBLOCK:100]
[NOFEAR]
[SIZE:200]
[ATTACK:MAIN:BYTYPE:GRASP:punch:punches:100:200:BLUDGEON][ATTACKFLAG_WITH]
[ATTACK:SECOND:BYTYPE:MOUTH:bite:bites:100:100:GORE][ATTACKFLAG_CANLATCH]
[EQUIPS]
[DIURNAL]
[BIOME:ANY_LAND]
[NO_DRINK][NO_EAT][NO_SLEEP]
[NO_GENDER]
[FIXED_TEMP:250000]
[STANDARD_FLESH]
[SWIMS_INNATE][SWIM_SPEED:0]
[CANNOT_UNDEAD]
[SPHERE:DEATH]
[SPHERE:STRENGTH]
[SPHERE:WAR]
Basically, if it works, you should have however many squads of nearly indestructible, teleporting, fire-breathing, monsters. Almost as scary as a river full of hippocarpephants.