Register renaming doesn’t significantly address the impact of reducing the number of architectural registers available to the compiler. With fewer register names available, the compiler will spill locals to stack more often, and register renaming doesn’t help - memory renaming is needed to really mitigate this.

But i agree the impact of preserving frame pointers is generally quite small and doesn’t often actually need mitigation - on amd64 there’s not much impact from losing 1 more of 16 arch registers.