force set, Gravity powers under it.

psychicslug

They need to do a subset with in the foce set called gravity, all the powers would be under force but more geared to a gravity bent. This means holds, slows, and crushing damage. Reverse gravity and others like floating or weightless effects. Whereas force would be focused on shields and knock backs and bashing damage, but could also be given slashing or piercing for some effects. even a large blade affect like a heavy weapon but criticals more easy and is faster as is made of force not a physical heavy substance. spike shield that like endgery matrix takes a few seconds to build up and then projecks long spikes in all directions causing piecing damage and knockback as well.

mysterygrayleaf

With the Champions RPG, they aren't subsets, just closely related powers:
"Force powers are closely associated with Energy Manipulation Powers, Kinetic Energy Powers, and Telekinetic Powers in many cases." - Champions Powers
"Gravity powers are often closely related to Density Alteration, Force, and Telekinetic powers." - Champions Powers

Closely-related powers generally mean you can re-flavor the others powersets abilities easily.
Gravity can rename/reflavor/re-use:
Force Shield -> Gravitic Shield
Personal Telekinetic Field -> Personal Gravity Field
Augmented Defenses (Density Alteration) -> Gravitational Defenses

With general offensive stuff, Force/Gravity both related to TK get to do this easily:
Telekinetic Blade -> Gravitational Blade // Force Blade
Telekinetic Mace -> Gravitational Mace // Force Mace

Subset-powers are like Fire's Smoke and Water's Steam:
Fire's Smoke:
"Where there’s fire, there’s smoke, so many characters with Fire and Heat-based powers also have some ability to create and manipulate smoke. Air-based characters may also have some of these powers." - Champions Powers

Water's Steam is a footnote:
"Another of the “elemental” power suites, Water Powers grant a character the ability to control and manipulate water — everything from generating powerful blasts of water to transforming one’s body into water. This category also includes steam-related powers." - Champions Powers

--- back to topic ---
With the game-game aka Champions Online: Gravitic Ripple, Gravity Driver, Singularity Bomb are already in Force. With Wind and Force technically doing reverse gravity. The only case is for proper attractive gravity. However, only Energy Projector has no melee, since EP lost Earth. So, Gravity has to be mainly melee if I know the devs right. Most if not everything sort of leans Gravity towards Earth/Might.

General flow (Melee Archetype) with Gravity FX:
1. Wield Earth -> Wield Gravity
2. Onslaught -> Gravitic Onslaught
3. Land Slide -> Gravitic Slide
4. Earth Form -> Gravitic Manipulation
5. Quicksand or Hypervoice -> Gravity Quagmire (Reverse Repel Sphere) or Pulling Wave(Reverse Repel Cone)
6. Force Control (Knock-based/Ranged) -> Gravity Control (Stagger-based/Melee)
7. Havoc Stomp(Knock Up) -> Singularity Stomp(Knock Prone or Stagger)
8. Stone Shroud -> Gravity Shroud
9. Destructive
etc.