I've usually started on the Spaceport before t150. But if there's a foolproof plan to get Sagan, Korolev and at least one of the +100% Great People, then that is indeed unnecessary. Maybe I should rethink my early game as well. I never build neighborhoods, except sometimes for Conservation inspiration in some city that otherwise cannot contribute to my victory, like in the Norway game. I've never built any sewers and so far I've only once built a regular aqueduct. Housing doesn't seem necessary and especially neighborhoods and sewers just don't have time to pay off in a fast game. With Colosseum there shouldn't be any need for Entertainment Complexes either. Amenities are quite easy to keep positive by trading actively for amenities from the AI. In 6otM 01 I didn't build any ECs either, despite not having Colosseum. I had 9 Baths in my 21 cities for some extra amenities, but that's not remotely as good as Colosseum.