Both of the currently supported platforms, C64 & BBC Micro, also had Z80 add-ons available which allowed running CP/M. I don't think the project is necessarily about it serving people better.
C128 CP/M is slow compared to other CP/M systems due to oddities of its implementation, but it works, it's native on the Z80, and with a 1571 you even get disk compatibility. In 80 column mode, it's certainly fast enough.