In that case, might I suggest Calyx: microG, privileged extension and based on AOSP, you won’t get more vanilla than that. Here’s the thread about it if you have more questions:
iodé could be an option as well, I don’t know if they include the privileged extension 
you’d have to ask someone who runs it:
(Side note, don’t lock your bootloader without checking fastboot flashing get_unlock_ability!!!)