Given the rarity that someone has pasted 100 000 rows into and want them to be autoborked disabling autoborking, at least for pasted data seems appropriate enough for me ;-)
Seriously? Also for pasted series? Also when the rest of the column doesn't match?
The I-want-to-put-data-in-my-table-which-closely-resembles-an-incredibly-common-format-but-is-problematic-if-mistaken-for-that-format-oh-and-I-can-not-be-bothered-to-google-how-to-turn-off-autoformat niche is not very large. I don't work for microsoft and I don't have copies of user data, but I would be willing to bet my entire life savings that over 95% of the time someone pastes a series which appears to have mismatched data types in the columns, the series actually does have mismatched data types in the columns.
I'd rather think of 100 000 rows where some of them looks like like a date.
Select format cells
Select "Text"
This will disable excel's autoformatting. Given the rarity that someone types "SEPT4" into excel and isn't typing a date, putting the option one level deep in a menu seems more appropriate than a top level button.