It is done in this way on almost any platform that is classified as mainframe. Originally one would IPL such platforms by manually toggling in either some simple code that would somehow DMA the OS bootloader from some external device. This was not exactly user friendly and replacing the front panel blinken lights with some sort of interactive monitor/debugger running on separate smaller CPU was common approach (for example many PDP-10s have PDP-11 in them used as "console processor").

For more recent systems (IBM mainframes, Sun/SGI large machines, etc.) the controller also handles things like power sequencing, hardware configuration (e.g. physical partitioning of interconnect buses, resource allocation...) and mainly also enforces the hardware licensing policies.