It would have taken real nerves of steel to pull off this alternative ending in the original Thief 2: The Metal Age, and for better or worse, would ended the series on a much higher note.
...With room to expand.

Original ending always bugged me by being empty, desolate and much easier than previous missions. The Builder's Paradise takes a deep dive into exploring what would have happened with The City at the end of Thief 2 were the Keepers not warn Garrett. Were the developers more willing to sacrifice the city itself to move the entire the series in the future, The Builder's Paradise demonstrates of the potential.

A promise of hidden machinist cities, a hope of restored world from the last seed - it all makes your mind race as to what could the future hold compared to returning back to taking an odd job to pay the yet another landlord.

I can honestly say Builder's paradise deserves its place on the pantheon of the top must-play missions out there. Would the community take charge of the franchise and collectively expand on the base game mission roster by adding alternative and intermediate campaigns of this caliber, the game would be much better off for new and returning players.

Lineup:
+ Terrific atmosphere, the horror elements aligned with System Shock and shifting patrol routes make an unforgettable experience.
+ Unkillable, homing adversaries is something an experienced taffer secretly yearns for and is terrified of. Delightfully uncompromising.
+ Stellar customization
+ Brilliant storyline