It's way more common than you may realize. Intel & AMD (and other x86 CPU manufacturers of the time) did it before the first Crusoe CPU launched. (2000 according to Wikipedia)
CISC architectures are now seen as inefficient, so all the new ones are RISC and new CISC CPUs just translate the instructions to their intenal RISCier microarchitecture. The CPU's microcode specifies what an instruction translates to.