Other than CPROM (Videomation mapper) and Squeedo, do any mappers have more than 8 KB of VRAM that can be bankswitched into PPU $0000-$0FFF or PPU $1000-$1FFF?
TQROM board (MMC3) could be interessting, it has both 8kB CHRRam and 64kB CHRRom.
I found the CPROM board very dummy, the feathure to swap ChrRam banks is interessting, but rombank swapping would be needed too scince having a lot of ChrRam is useless if you have a so little PRG space. The same swapping ChrRom would be interessting, it would be like CNROM with hardwired sprites or BG so it would allow an early game to have lot of sprites and simple BG or the opposite.