Note: Speculative/filler values placed in [brackets].
The whole concept I'm thinking of here is sort of an inverted power building mechanic, such as what exists with Nidus and Ember. Instead of building up power, you would be trying to keep power up without falling apart or exploding.
Passive: "Replaceable Parts"?: [Frame Name] has five (5) [100HP] segments of gated health. Upon losing a full segment of health, [frame name] is invulnerable for [ten (10) seconds]. Each missing health segment increases movement speed by [10%]. Healing over time or area of effect healing only heals within the active health segment. Picking up a health orb (see Ability 1 note) or certain abilities are the only way to replenish a missing segment.
Ability 1: "Retrofit"? "Field Repairs"?: Press the ability key to tackle the selected enemy and strip them for parts, doing damage equal to [frame name]'s total missing health in the process. A health segment is instantly recovered if the target dies. Optionally, pressing and holding the ability key does the same, but will also temporarily rig a special weapon to [frame name]'s left arm. Pressing the ability key after the retrofit will use the given weapon until replaced or duration runs out. Holding the ability key without an enemy targeted releases the currently attached special weapon.
The weapon type depends on the enemy attacked:
-Grineer enemies grant a slow-firing, target seeking rocket launcher that does scaling heat damage with 100% status chance.
-Corpus enemies grant a tesla grenade launcher that launches electrified sticky grenades. Stuck enemies take scaling electrical damage with a 100% electrical status chance. May chain to nearby enemies.
-Infested enemies grant a tentacle whip that knocks down enemies in a frontal cone area of effect. Affected enemies are leeched for life on hit and deal scaling toxin damage.
-Orokin enemies grant a crystal (ice spike) launcher that glasses (freezes) an enemy on hit. Shattering a glassed (frozen by ice spike) enemy causes scaling freezing area of effect damage with a 100% status chance.
-Sentient enemies grant a laser prism launcher. The laser prism will hover above you or a targeted friendly player, npc, or objective upon activation. Does scaling tau damage with 100% status chance.
Ability 2: "Tactical Ejection"?: [Frame Name] sacrifices a segment of health and removes any current status effects. Shrapnel fires out from the frame in a [10 meter] radius. Shrapnel inflicts damage equal to the sacrificed health and of the damage type that was removed with 100% status chance.
Ability 3: "Soul Meld"? "Integration"?: [Frame Name] molds himself into an exoskeleton around the body of an enemy or ally, draining energy over time. Targeted allies gain [70%] damage reduction and [frame name] manifests a 3rd arm on the ally's back that he can control to fire their secondary weapon. If the ally takes lethal damage, [frame name] is forced out of the ability, but the ally instantly recovers to 50% total health. Allies may roll dodge to force their way out of the ability, forcing Targeted enemies have their health leeched over time instead of receiving damage reduction, and will become completely controllable. Controlled enemies gain higher, level-based scaling damage output for the duration of the ability. If the controlled enemy dies, [frame name] recovers a health segment and transfers to the next closest enemy.
Ability 4: "Void Stitching"?: [Frame Name] sends void tendrils in all directions, tethering all enemies in a [5 meter] radius, and rapidly ragdolling them all back to him. After 2 seconds, [frame name] sacrifices a segment of health and releases a massive blast damage explosion, dealing out damage equal to the HP value of the sacrificed segment multiplied by the number of tethered enemies. This ability costs no energy and activates [frame name]'s passive ability upon sacrificing the health segment.