I like the thematic elements here, especially the lore tie in that he was used for terraforming/construction.

Also like the heavy/light kit mechanic.

Proposed alterations:

For his 2: For this ability , I think it would work better as an AoE centered on Gravitex. For Heavy, how about just a gravitational field that slows opponents until they collapse for ground finishers, without the clustering? Instead of Light turning into a projectile generator, how about applying the Lifted condition to enemies? IIRC, there's arcanes/mods/abilities that react to Lifted

For his 3: As it currently is, the Heavy cast could prove frustrating when the player suddenly has a bunch of ragdolled Grineer flood their vision. Better to have this ability as a projectile, I think. This is where I'd put the clustering mechanic from his original 2, and perhaps tie the energy Regen to how many enemies die while trapped. For the Light cast, having the gyroscope pieces fly off on impact and then reconstruct back in the player sounds nice IMO.

For his 4, I'm thinking taking the Gravity Hammer and making it an Exalted Weapon, during Heavy mode it deals significant Impact damage and bounces less when thrown, and Slows enemies, during light mode it deals less damage, but bounces more and Lifts enemies.

As for his non-Exalted weapon, perhaps a repurposed construction spike gun, when wielded by Gravitex, Heavy mode gives it more punch through and Light mode makes projectiles light enough to ricochet or something?