I played around with the S2152 some more, and I was not able to get it to change banks while in "verify internal ROM contents" mode. So it looks like "override bank 0 with external program" mode will be needed to get those extra 512 bytes. I haven't found any schematics showing an external ROM connected to an S2xxx, so I'm not sure if an address latch is needed.

I got a 1978 Waddington's 2001 The Game Machine. It has a 3870, so I should be able to dump the ROM: MOSTEK 3870 MK14154N Malaysia 2001 7909