I think that at this point many people consider "mentally unstable naive farmboy from flyover state" as a core characteristic of Superman.
This reminds me of what Tynion said (if I'm not mixing him with someone else) about 90s and how many of the current writers grew up reading comics from that era. How long before we start getting writers and artists for whom Injustice Superman is the Superman?
As for mandates on what to do and what not to do... You might say how Waid's Irredeemable has something interesting to say, but he still decided to do an evil Superman story in the first place.