Quite happy with the endings now. The old ones just really didn't make sense. I also liked
shooting at that stupid child triggered the new 4th ending. You could also get it via Renegade dialog options.
The one big F-U the developers put in was disabling the ability to skip dialog and autosaving once you made your final decision, forcing you to sit through the 30 minutes of buildup all over each time you wanted to see the extra endings.
No, you don't have to restart at the Cerberus base each time.