Though in practice the reason we have Jesus is so we can ask "What would Jesus do?", which is easier to answer than "What would the ideal rational agent with unlimited computational resources do?".

In Stoicism, we call this type of person a sage. It is actually a very practical concept to make use of. During before-sleep meditation, I'll playback my entire day in fast-forward mentally, but alongside me I imagine a semi-transparent sage-me and I "watch" as our two paths diverge (with the sage-me living a perfectly virtuous life and me falling far short).