Mine dispenser pod (see the helix bombs, OCL a cluster mines bomb instead of a helix bomb).
Leaflet pod (again, can use the Helix style of doing things, else use the smart bomb style. see below)
Smart bomb upgrade (loads the plain's transportcontain slots with
smart bombs which you exit over the target area)
Laser target designator upgrade (adds a portable structure like the helix gattling, that fires the Avenger's laser designator, that makes other units fire faster at the target)
Your ECM pod upgrade could also grant stealth to the plane (since it jams enemy radar), in the manner of the GLA base defence buildings that can be upgraded with camo netting. It could also add a portable structure which fires a jamming beam like the Microwave Tank, to jam enemy base defences.
Decoy drone upgrade, spawns a decoy drone that flies near the plane, drawing enemy fire to itself.
EMP bomb upgrade, either helix style or container style, add an EMP pulse bomb. However either make the plane KindOf EMP_HARDENED, or make the bomb take several seconds to OCl the EMP spheroid else the plane dropping it will be caught up in the blast and crash.
Frenzy upgrade, spawns a frenzy marker at the plane.