Some of these may exist. I haven't searched every power in every set. Most of these have probably been suggested elsewhere, but here they are anyways:

1. Growth. Having large/giant size heroes is fairly common in comics, and you already made Grond that large. Why not others? They can have the same disads/ads that a Grond would have as far as reach, AoE melee, easy to see, can't be missed at range, etc. Travel power would be the only difficulty I can foresee with this, as you don't want a flying giant. Strength scales with size.

2. Shrinking (bet you knew that was coming). Reduced threat range, increased evasion, restricted movmement (treat it as if affected by a movement debuff). Again, it utilizes things already in the system.

3. More options to name carrier attacks. Gadgets/ammo don't always give energy/crushing/piercing damage. Poison and bleeding damage from, say a fragmenting grenade, or tear gas type grenade. I could very well be wrong; but so far, the only "poison" I saw was associated with fighting claws or breath (supernatural). Both have distinctive sfx.

4. NND damage that (since it could be hard to simulate that with the current defenses set up) is either penetrating or armor piercing to anyone without invulnerability or forcefield (to name two possibilities). The defense can be chosen at the time of power selection.

5. A gravitational power set. Some of the stuff would cross over with Force power set, but here are a couple of sugggestions to make a completely separate set. Holds that don't have physical sfx, and don't lift the victim into the air; if charged fully even do damage over time until broken. A high knockback melee (disproportionate to STR) to represent a change in density or manipulation of gravity. An AoE telekinetic effect, as multiple objects are affected by loss of gravity. Note they wouldn't be able to "throw" anything; simply lift/maintain, and then drop -- though that could certainly do some damage, lol. A tractor beam type pull power, with sfx that don't show some chain or thrown ninja weapon, or other such thing. Just an energy beam sfx, and a limited range.

6. Random effects. That is, a power that when activated doesn't necessarily have a random secondary effect (which already exists, IIRC, but random secondary targets in an AoE. It increases collateral damage, but might make a hero more careful about using the power if a penalty to acclaim/reputation was applied with increased damage.

7. Penalties and vulnerabilites to certain power sets in certain maps, or on certain missions. For example, reduced damage/effect from ice powers in the desert maps, and maybe even DoT to character; The same for fire characters in the underwater missions or on the canada map. Vulnerabilities to mystic attacks by those who choose Supernatural/Celestial; vulnerabilities to technology/melee weapons for those who take arcane powers. Again, it seems to me that such things already exist in limited scope (particularly the DoT on the map) -- they just need to be expanded and honed.

8. The ability to give certain restrictions to the Nemesis set. For instance: Your nemesis may be fire based, but they don't necessarily fly (pyro is a perfect example of a comic book villain). More on the nemesis in a different thread :)

9. STRONGER NON-DAMAGE BASED MENTAL POWERS! I realize that CoH was unbalanced with regards to mind control; but it seems to me that you have gone on the other end of the pendulum here in this game. It is almost impossible to make a subtle character/mentalist that works in either PvP or PvE (all super villains seem immune to placate, confusion, and ego hold in my experience, and Master villains are overly resistant, and none seem to work in PvP because of the charge time) One possible advantage to give them without changing actual strength or effect would be to make them line of sight, as they are in the pen and paper game. The greatly increased range would allow for time to charge those powers that need chargaing, and not make the hero immediately subject to mobbing attacks. I had to give my mentalist Ego Storm (a really cool power, but not fitting the concept) just to make her survivable since hitting one henchman draws all of them in the group, regardless of facing. No picking off people one at a time in this game, lol! It also restricted my item selection, since I had to favor CON/PRE bonuses -- again, just to survive. I originally tried EGO/DEX bonuses since it fit the concept of Critical damage overwhelming an opponent, but would taken out too quickly by buddies while destroying my current target. The idea originally was for stealth, manipulation, and more subtle game play.

10. An illusion-based power. Since you can summon nightmares/dopplegangers, etc. how about non-offensive images that reduce threat or increase evasiion, etc. to represent the suddenly confusing increase in possible targets? Or an sfx that makes your character appear like an NPC/citizen, and takes threat to zero (like smoke grenade, only showing reflections of you)? It could even work in PvP, given the right settings and flexibility of image (such as some furniture or landscape item for instance. I realize looking like someone on the opposite side is pretty much impossible, given the flexibility of character appearance -- which is really cool, btw :D)

Hope this isn't too much at once. I look forward to your responses.