The problem with an 8-bit CPU like the Z80 will have a hard time to control all that hardware. Indeed, KAI magazine, who make lots of games that support both the v9990 and OPL4 state exactly that.
Yes, I agree. That's why I specced the 6809/6309 instead of the Z80. Clock for clock the 6309 is nearly twice as performant as the Z80 even though it's also an 8-bit CPU.