I'd think a cannon like this would be a ton unbalanced; the EMP would shut everything down, and kill it without resistance.
Put TypeImmune=yes to be able to repel friendlies of its own kind
The rest isn't a unit, it's a weapon entry. Give it to whichever unit you want by using the Primary= tag.
Primary=Emp155mm
without testing, this is what I came up with. Basically, I cloned the exsisting artillery weapon, and made a new warhead for it, with EMeffect.
You'll have to test it, I'm feeling lazy right now :tongue:
If the game crashes when the weapon is fired, then I must've done something wrong

CODE
[Emp155mm]
Damage=50
ROF=150
Range=7
MinimumRange=5
Projectile=Ballistic
Speed=10
Warhead=EMPHE
Report=120MMF
Anim=GUNFIRE
;Lobber=yes
[EMPHE]
Spread=3
EMEffect=yes
Wall=yes
Wood=yes
Verses=100%,85%,70%,35%,28% ; changed conc from 10%
Conventional=yes
Rocker=no
InfDeath=2
AnimList=XGRYSML1,XGRYSML2,EXPLOSML,XGRYMED1,XGRYMED2,EXPLOMED,EXPLOLRG,TWLT070
Deform=10%
DeformThreshhold=300
Tiberium=yes
Sparky=yes
Bright=yes
ProneDamage=70%