A simplified CopyNES was sorta what I was going for. I do like the MAX202 idea, but I am trying to keep this as simple as possible, and most of my hardware interfacing experience is with the parallel port. I do see how the Parallel port protocol can get quite complex, but if you can understand how NES registers work, then you can write a protocol that'd work between two natively incompatible systems.
There are ways of making a unidirectional PC->NES interface using a Zener diode and resistor (no MAX232 chip needed), if complexity is a problem. I suppose an optocoupler could be used instead, for extra protection. The NES can be made to work with most serial systems, without needing a UART. The problem with parallel is that it places heavier timing requirements on the PC software. The NES side is fine. Funny how now it's the old stuff that's more flexible :)