The open() function is very commonly used, so modifying it requires a lot of discussion. In Python, we prefer to discuss such changes ("feature request" if you want) on python-ideas, rather than on the bug tracker, to get more reviews and feedback.

open() modes and os.open() modes are very different. IMHO it's ok and simple to add enums for os.open() modes, but I'm not sure about open() modes which are strings. I don't think that enum supports mode1 | mode1 if mode values are strings. Moreover, for backward compatibility, enums should behaves a the str type. I don't think that it's possible neither, whereas IntEnum would fit nicely for os.open() modes (integers).

Usability and backward compatibility deserves a long discussion.

Note: there is python-ideas mailing and the Ideas category of discuss.python.org. I'm not sure which one is preferred.

https://mail.python.org/mailman3/lists/python-ideas.python.org/
https://discuss.python.org/c/ideas