Ouch. That was kind of rude. This IS the script request forum.
I'm sorry but this is such a BS excuse, I'm sick of seeing it on this forum

Minor aesthetic changes can greatly make a game seem more authentic, especially when trying to emulate retro games. I appreciate the request of a more authentic retro screen fade; every little thing counts. Honestly I dislike when retro games try to "look" retro but there are so many technical things that breaks immersion and says, "oh, this is actually just a modern impersonation of a retro game". Smooth fade transitioning would definitely break the immersion for an NES-like game.
Personally, I
would use common events,
but in OP's new thread he specifies that he's already using a lot of common events and therefore doesn't want to lag the game anymore. Perfectly understandable.
OP, if no one is willing to make a script (which is also understandable; people are doing this out of charity, so they are not obligated) then I do recommend finding out a light-weight way to make a common event; perhaps you can only activate it with a Common Event Call, instead of running it all the time with parallel process. This should make it so that your game won't lag or crash.