Go beyond that and the power usage balloons quickly (won't repeat myself, see my other comment on this thread at https://news.ycombinator.com/item?id=25231798).
On laptops, more power efficiency maps directly to increased performance (turbo clocks provide higher performance in bursts or at the expense of your laptop's fans sounding like a jet turbine).
Oh yes that would rock and open up a whole new level of fault tolerance as could run real-time upon two different CPU cores in parallel, which for some workloads would add value.
Certainly adding an ARM chiplet would be cool and technically doable, though so would a RISC V core and if Nvidia buy ARM then that choice may become political.
If? Was that a typo? They have indeed [https://nvidianews.nvidia.com/news/nvidia-to-acquire-arm-for...]
Now, if only AMD could bring back that ARM Zen design that they cancelled a few months before Ryzen 1st Gen...