Earlier today I found a way of skipping straight to Babel as the first monument. It requires starting a new file without a memory card, then inserting a memory card with 15/16 monuments completed, and loading the monument progress to the new file by entering the monument list menu. You stay on the same map, but monument progress and various other things (such as time of day) copy over.

See it demonstrated here:

I only experimented with it a little bit. I'm not sure the full extent of what is possible, or what exactly is required to get this to happen, but I will provide my current setup so people can reproduce the trick.

1. Boot the console with no memory card inserted.
2. Start a new file with no memory card.
3. Open and close the monuments list.
4. Insert a memory card with 15/16 monuments completed.
5. Open and close the monuments list.
6. Remove the memory card.
7. Insert a new memory card to progress to the final island after Babel is complete.

I think there should be some discussion about how to deal with this as a category. For now, I have named my run of this "Any%" and renamed my previous runs to "16 Monuments". I think "All Monuments" sounds better, but would imply getting both the love and hate variations for each monument.

Alternatively, I think another option would be to create new cateogies for each of the maps, and the old Any% category would become a new category simply called "Barudo Island". The rules could be changed to start from the new map menu; afaik the only difference is not having a cutscene which you can skip anyway, and it keeps you from having to keep deleting your save data whenever you reset.

Any thoughts or input from others would be appreciated.

Great find! Honestly, I think this can't be considered Any% as it relies on using a prior save for its strategy which across speedrunning has historically been separated into its own category. I'm open to discussion about using the memory card to skip the opening cutscene as Super Mario Sunshine eventually allowed that for its Any%, but as you've said, you can skip that cutscene anyways. I understand how much deleting save data on resets can be a pain (looking at you, Devil May Cry 4: Special Edition), but Doshin is a glitchy game that breaks with little effort or accidentally (to say the least) and I am hesitant to allow this for Any% until we know more about how it works and I (and other mods and players) can feel confident in it not having some unrealized knock-on effect that changes the game behavior.