with that route i think you're almost better off doing your save-and-reset idea rather than spend that much time killing all those enemies...
here's a super fast route that's really only appropriate for segmented... you get to the final battle with 30 missiles but no resonators. also the area up along the southern wall is super glitchy and more often than not you get wedged against a wall and have to reset. but start the final boss cutscene at around the two minute mark, meaning sub 3:30 comet should be possible :O
edit:
and here's the missing southeast launch. the fastest yet and luckily it's super easy. very similar to the original launch in the northwest. i suspect the level geometry might have just been copy and pasted over.
here's a super fast route that's really only appropriate for segmented... you get to the final battle with 30 missiles but no resonators. also the area up along the southern wall is super glitchy and more often than not you get wedged against a wall and have to reset. but start the final boss cutscene at around the two minute mark, meaning sub 3:30 comet should be possible :O
edit:
and here's the missing southeast launch. the fastest yet and luckily it's super easy. very similar to the original launch in the northwest. i suspect the level geometry might have just been copy and pasted over.