SignOfZeta, you don't know what you're talking about.
First off, even without any mappers, the Famicom is a generation ahead of the Coleco, outperforming it in terms of resolution, colours per tile, maximum colours on-screen, and total colours available.
But to the issue at hand, the Famicom is limited graphically, but it extends its PPU (graphics chip) bus to the cartridge connector, making it greatly more expandable than systems that didn't. Unfortunately, the PCE is in the latter category. All that the HuCard connector can access is the CPU bus, meaning the only thing extra chips in a HuCard could offer would be more ROM or RAM. No graphic enhancement is possible.
The expansion connector is another story, though. Devices that enhanced the graphics of the PCE would be feasible (but don't exist(?)), and sound is obviously already well-supported by the CD attachment. But sorry, special chips inside HuCards would be useless, IMO.