On the off chance that you haven't yet looked at smalltalk, can I recommend cuis smalltalk as worthy of investigation.

It's a simplified smalltalk (like pharo, forked from squeak), where the emphasis is on having a base system that you can reasonably fit in your head (think scheme vs common lisp).

Here you'll find much of what you described, including per-method revision history.

BTW, it comes with a rebuilt morphic gui with flawless scaling - unlike most smalltalk, this one actually looks crisp - even on large displays