[Multiple worlds + collector's mentality + base building + female protagonist (non-human) + late-game troop buildup + system that's just going through the motions]

Ostro, a transmigrator, looked around and thought he had been reborn into a high-tech era, until he discovered Terra, Eldar, the Martian technological world, and the intelligent legions in his memories, and then he burst into tears.

Good news, we're in the Golden Age (dark technology); bad news, the Iron Man rebellion hasn't happened yet; good news, my parents in this body have some assets on Mars; bad news, they're both dead and I just cried myself to death.

Until the system delivered the gift pack, making me feel invincible with the cheat, and then the system, having delivered the gift, simply left.

At least it gave Ostro some hope, didn't it?

then:

Cult of Mechanics: How does he always manage to retrieve the complete STC template? He must be a Chosen One of Ohm Messiah.

Primal: A powerful, loyal, and resource-rich sage. We should try to get along with him. He has no other flaws except that he sometimes likes to steal the power armor from his minions.

All Astartes: Do you still want the power armor I just DIYed? You promised to trade it for 10 Terminators, can you still do that?

Tarasin: You're stealing my loot! Fine, you took my spoils, but how did they end up in my house?

(This is a new book by a new author, please forgive any shortcomings!)