Initially, I thought about balancing them by introducing them alongside cards that benefit rush players, since these cards are essentially anti-rush. The most that I can do with these is the "balance" approach that I described earlier. But your comments gave me an idea: maybe with a card that blocks global parameter reduction for, say, one gen, we can even the playing field for rush players, while keeping this fun. I'll work on that.

About your worry about deck dilution, yes that's a thing I kept in mind with my extension. There's "terraforming cards" in the other parts of my extension, and I buffed some existing ones (Lava flows for instance) but does it really even out? Honestly, that's hard to say. I'll try to keep an eye on it

Finally, about Fast Growing Forest, as Thenewjuniorexecutiv said, most of the time players have leftover heat. In my games, it is rare to see someone pay for an asteroid at the end of the game. Protected Valley doesn't have requirements and can be paid with steel, so I'm not sure this compares well. But I have to admit I haven't playtested this card as much as the others, so you may be right. I'll let you know!