I'm thinking of several new mods to be added for TFTD:
Tentaculat on land and sea: this dreaded foe can be found above and below water. Its flight only works underwater, but it poses a major problem in a terror mission, potentially turning civilians into zombies.
Surface alien craft and alien colony missions: since alien craft cannot be shot on the surface but can be intercepted when it lands, I believe that there should be new battlescape maps of those craft on land. Also, some alien colonies are on land as well so both parts of colony attack should be land based. Of course, expect to find land terror units on colonies and some alien craft.
Sonic Pistol Auto: as the name implies, lets make this sidearm have an auto function, though the rifle and cannon remain aimed and snap.
Ammo for Sonic Displacer and Sonic Oscilator: ammo must be manufactured for these; the Displacer uses Sonic Shells and the Oscilator uses Sonic Oscilator Rounds. Both require Zrbite and both are manufactured in clip fashion rather than singular.
New M.C. Power: Cripple Implant - an offensive power in similar fashion to mindfray, easier than Control implant, harder than Jam implant. If successful, the target takes health damage, ignoring armor (no fatal wounds) and reduces stats and morale like any other wound. Furthermore, the target's M.C. Strength is reduced temporarily, leaving him/her/it more vulnerable to M.C. powers. Of course, Cripple Implant can kill if used enough times.
New Ammo for torpedo launcher: Rocket Torpedo - this torpedo variant incorporates a propulsion system that can be fired over land as well as underwater, whearas most other torpedoes can only be launched underwater.