usernamed I hope that oneplus will also be added to officially supported phones.
They will never be supported until they meet the GrapheneOS hardware requirements, and even then its not guaranteed: https://grapheneos.org/faq#future-devices
Moreover, this will enhance the security of oneplus users.
No it will not, that burden is on OnePlus, not GrapheneOS.
usernamed Google itself is not perfect
Sure, but Pixels are more secure than OnePlus devices, because Google actually cares about security.
usernamed I think it’s not a bad idea to introduce support for 1-2 devices (even with partial support)
You're right, it's actually an atrocious idea to partially support 1-2 devices.