Today I’ve gave a look at the Sony SMC-777 HW again. The system uses a “timed” bankswitch, presumably involving instruction pre-fetching.
For example (this is BIOS ROM code, located at 0x0000-0x3fff):
3BF3: 3E 10 ld a,$10
3BF5: D3 1C out ($1C),a ;enables RAM bankswitch
3BF7: C7 rst $00 ;executes this, then switches to RAM mode
Enabling this and adding the unimplemented features makes all of the available programs / games to boot properly with sketchy keyboard and some games with imperfect colors (presumably missing clut):