Sharp MZ-2500 emulation should be enoughly good now, there are still a bunch of unemulated features but they are hard to test them out with Dust Box games (it requires a lot of time with current fdc timings) so I'll pass for now.
Anyway new day new driver (with some hara ... help from Charles MacDonald ^^'):
r9059 /src/mame/video/vdc.c: [PCE]: Fixed sprite OV flag behaviour, fixes Mizubaku Daibouken hangs