I think i remotely read somewhere that the snes and the n64 cic's share some similarities. Is there a possibilty that with the knowledge that now is known from the super nintendo cic's and n64 cic's, that a n64 chip could be made? I would love a region free n64 with 50/60hz feature as the superCIC for the N64? I guess it's a lot of hard work and tinkering, but I just figured that I could ask at least, if anybody is working on it.
People will most likely correct me if I'm wrong but I'm pretty sure the N64 CIC is much more advanced than its SNES counterpart and can receive different challenges and responses depending of which revision of the chip the game use (several revision). There was some CIC that were sent and decapped at http://www.retroactive.be/cic/ and I also think the algorithm of the chip were reverse engineered for emulation purposes but I don't think this is something you'll be able to easily replicate with a simple PIC microcontroller like the SuperCIC (maybe with a small CPLD?). But you should wait for other more knowledgeable peoples to answer your question though as I am far from an expert and those are just educated guess using the best of my knowledge on the subject (that's not saying much 
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)Unfortunately N64 uses software control 50hz or 60hz, like the PS1/PS2 and newer consoles. A traditional switch similar to SNES/etc very likely isn't feasible.