Of course it simplifies the design if the CPU is clocked by the CRT controller.
But the point about the D04 CRT\LCD controller is, that it's a passive device snooping the CPU bus for write cycles.
Means: no matter if D04 is present in the system or not, the CPU just works.
Also, D04 doesn't mind changing the CPU clock frequency from 1MHz..3MHz.
...And in theory, it's possible to hook more than one D04 to one CPU.
One could implement that in two CPLDs, but to put it this way:
Some time ago I had some bad experiences with CPLDs which had _brought_ me into TTL tinkering.