In all probability, yes. I'm not sure how much easier it would be to develop though. Back then, most (if not all) of the operating system was developed in assembly language while there was far more to consider when it came down to performance and memory usage (which is often in conflict with each other). CP/M was also notorious for running on hardware that was incompatible with each other, relying upon the BIOS to smooth out those irregularities. While that may simplify the development in some respects, such as the hardware vendor developing hardware drivers, it complicates development in other respects, since CP/M development could not make assumptions about the underlying hardware.

There's some really great documentation out there on CP/M, Kildall struggled initially with the hard disks. While large parts of CP/M were written in assembly, parts were written in PL/M as well.