Heresy! 
ISA's were perfected when Motorola designed the 68000.
I think it was you Matt that once said that AMD should have "Athlonized" the 68k and not the 386.
I couldn't agree more with that statement.
Now where did I put my pipe and slippers?
Definitely sounds like something I would have said, a search on this forum will provide evidence

I think Athlonising the 68k would have been amazing, but it would have lead to similar problems that both intel and AMD have now... Lovely computing performance but at a terrible thermal and electrical cost

Though it would have given us a solid platform for development... Look at the new ARM v8 ISA, it's actually a bit nasty compared to the ARM v7, but it was developed after analyzing real code output from compilers and seeing how to get serious performance in a low energy budget

-edit- Forgot to mention that I have an ARM v8 chip here, and it is something else in performance... In a phone too!!! :-D