For AI difficultly, I’m sorry this is not SC2, if the default behavior of the built-in AI that lasted 23 years has changed, this won’t be SC1 we know + Blizzard won’t do it since its already done by BWAPI community, they just need to fulfill there promises and make SCR compatible with BWAPI.
For stronger/weaker AI compared to the built-in one, you can check BWAPI Revamped.
For external/offline replay viewers like BWChart, you say by yourself “external”, how you want Blizzard to do that, since its also already done by the community:
https://repmastered.app
https://scbw.gg
Also for internal/online replay viewing, nothing beats the CoachAI replay system yet, not even in SC2.