So many planet transformers, I think there's enough already, but it looks like metallic and icy planets have the lowest amount of transformers: Metallic: 1 (Dyson Transformer) and Icy: 5 (Mass Surface Melter). Exotic planets don't have one, probably because the natural resources can be mega rich+.
I'd like to suggest a CTL blueprint (if not: mission after potent residuum) for metallic/icy transformers.

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Metallic --> Rust
Size: +1
Resources: Choice: +2 Mining, +1 Artifact and Research -or- +2 Research, +1 Mining and Artifact
Passives Gained: [Permanent] Rusty Atmosphere - The airborne rust particles amplifies mines within the atmosphere, boosting planetary attack by 12%. (Would look like "Flux Storm" lightning animation colored orange/yellow)
Recipe:
1. 1 Phasic Chain-Ionizer - Modify existing transformer
2. 250 Longevity Serum - Alter ionizing process to ionize oxygen
3. 200 Planetary Time Vortex - Speed time for oxygen/metal reaction

Limits: The rust on the ground and in the air prevents more population structures to be built. - Researchable Population structures cannot be built.

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Icy --> Permafrost
Size: +1
Resources: Choice: +2 Research, +1 Artifact -or- +2 Artifact, +1 Mining
Passives Gained: [Permanent] Permafrost - Permafrost just under the planet's surface keeps the ice on the surface intact even under heavy fire, increasing planetary defense by 12%. (Would look like icy version of "Subterranean Caverns")
Recipe:
1. 1 Thermionic Intensifier - Modify existing transformer
2. 250 Positron Clouder - Cloud the planet to cool it down even more
3. 200 Calming Amplifier - Calm the "Intensifier" of the transformer so planet doesn't explode or freeze too quickly

Limits: Cold conditions hinder population growth. - -60% population regeneration.

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Exotic --> Void
Size: +1
Resources: All +2
Passives Gained: [Permanent] Void Dimension - The planet repeatedly fluxes itself between regular space and a hidden dimension, increasing planetary cloak by 7%. (Would look like a black/white version of "Stealth Screen/Reactive Barrier")
Obtained:
Hidden NPC Blockade - Exotic-Specific Blockade (Massive cloak)

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I tried to think of ways to balance the resources and the effects it gives as well as the lab recipes (Because of modifying an existing transformer from the CT-Lab, the cost is even more than what I suggested after it). I'm all ears to all criticism, positive/negative.

When thinking about a "metallic" planet i think about that planet that is very rich in metal ores (not the ingame very rich) and that does not rust..

Other than that.. +1

I think that this is a great idea gives more people a chance to upgrade some planets they thought were useless and I think you put alot of thought into this . +1

+1 because I want something to transform my metalic planet..

For metallics maybe upgrade them to robotic planets? Just throwing that out there. Love the ideas +1 to them all.

+1

We need more planet upgrades in the game.

~JF~

+1 love the void planet idea, yet would need to be developed.