Mildly myself. I never owned an N64 game that refused to save on anything but the cart but I had plenty that could optionally use a memory card of sorts. Very few games absolutely required a memory pack for primary and sole saving from I can recall. Looking at the list linked above showing the usage of save locations I can tell you flat out that Perfect Dark does use it's cart to store save data and can load saves from a memory pack. Alternately the memory pack can be used to move saves around from cart to cart or as backup. The latter of which saved my butt at least once when the edge connector got a hairline crack somewhere.
If it had a battery, it used SRAM. That would be ideal for the feature proposed for EverDrive to automatically load and save controller pak saves for each game. EverDrive for all systems except N64 use FlashROM, not EEPROM. FlashROM is like EEPROM but it has a much greater lifespan I believe. Something anywhere from 10,000 to 100,000 write cycles I think. I wish MD EverDrive had a version using RAM (for both Game and Save Memory) just so you wouldn't have a write cycle limit. But realistically the lifespan is so high it shouldn't be a problem.
I have one of those third party Memory Cards, but I haven't gotten a chance to use it yet. I don't have my ED64 yet. But I'd like to copy my WWF No Mercy Save from my original N64 cart to the memory card, and then from the memory card copy the file to the WWF No Mercy ROM on my ED64, so that I can have all my saved games and created characters on my ED64. A. Does that make sense? B. Does that seem possible? C. Is No Mercy working with the ED 64? Thanks!
