Sugestions for infested dragoon- opens hatch, hurls out its infested soupy essence in a plamatic explosive charge, and the empty shell collapses into a pool of blood.
Wraith can plant a set amount of explosive bombs.
Battlecruiser can hold wraith or other fighters in its hull and slowly heal them
New units- Terran Helios- a large bomber that hurls large splash, high range. magma charges. looks like a sci vess hybridized with a bc and carrier+shuttle.
Terran Airflyt- Small modded wraith to look like the one here:

acts like a smller, fiercer valkyrie, relentlessy swarming units and unleashing random stalker homing missile spurts along its Torture spread lasers. Can be used as a bomb, bailing out a terran pilot who you can turn into an biological unit, and bombing a target. Easily destroyed, however, and works much better in swarms.
Terran Assasain- grp should be like a ghost crossed with a civ, but permanently cloaked, can take out lone units by using its "slay" spell that makes it go very close and play a random animation of it killing the unit in some way. Can sabotage buildings, causing high damage and making the building continously lose hp.. Expensive and long build time. has some long ranged combat ability with its sniper. kill spell effective only on units that are relatively alone.
{sorry if this is too complex for u, this is way beyond my league too, im just suggesting. BSTRhino could help u with this}
http://tc.brutkrieg.de/customs/customs.php?game=1 has good grps, like the one i showed u for t3h airflyt.
more later