yeah does look like I'd expect IMHO
a Seibu custom, 4 roms in the BG one (2x tile data, 2x layout data) what is probably a colour lookup PROM and some logic.
a Seibu custom, 2 roms in the SPR one, what is probably a colour lookup PROM and some logic.
Air Raid ones would be interesting for comparison, as I'm more certain that those do contain a colour lookup PROM.
I guess also an xray of a SEI0010BU which I guess is the seibu custom inside might also be interesting for comparison.
hopefully these will help the guys trying to work out a way to read them at least, I suspect it's going to take some drilling down to where the connections are and reading out each ROM / PROM manually tho, which won't be easy, especially without knowing what each pin is, which I don't think you can work out even from the xrays. I don't envy whoever has to dump these.
I doubt the raw data is exposed along the edge either, so to emulate it properly the content of each relevant die will be needed.