My motivation for wanting a relevant and useful Geoengineering mod is because of how (reasonably) powerful the 2/2/2 Research points from the 'Geoengineering Complex' is and how interesting the Building pictures look; it adds variety in a useful way.

Just because the Mod and it's buildings are now obsolete and redundant to their original purpose doesn't mean it still couldn't potentially still be use to facilitate Terraforming as intended.

Here's a list the ideas I have for how a 'reincarnated' Geoengineering Complex could work:

• One per Planet unique (if it isn't already)
  
• A slight bonus to drawing and research speed of 'New Worlds' techs (fraction of Scientist with 'New Worlds'), as I personally want fancy new research building and this seems like the best way to have the buildings help with getting Terraforming abilities.
  
• A "Geo/Terra-forming Reactor" upgrade that decreases Terraforming and Tile Blocker time and costs on the planet and gives a smaller Empire-wide bonus, with the cumulative being capped at 50%, 25% or something. (Dubious on how good of an idea this is for Terraforming due to how Traditions and Ascension perks can massively improve these anyway.)
  
• For Lore-Flavour reasons, the 'Mastery of Nature' and 'World Shaper' ascension perks provide individually a Unity point bonus, as well as some sort of locked/gated Upgrade unique to those Perks.
  
  Hope this facilitates making another interesting Building set to add into Stellaris.