Someone previously suggested this with Superstar Saga, but I'd like to see Super Mario Bros. Deluxe in English with all the QoL improvements from the later-released Japanese version.
That was my post you saw, I suggested a hack for SMB Deluxe that adds all the improvements from the Japanese version and a hack for Superstar Saga that restores the unused Starbeans cameo appearances along with adding all the improvements from the Japanese version.
Ninja Warriors (SNES): A hack for the international versions that will restore the female enemy, her sprites and actor ID are still in those ROMs, including restore the missing blood as well.
Splatterhouse 2 (Genesis): A re-translation hack that will change the plot to be more closer to the one from the Japanese version.
Teenage Mutant Ninja Turtles: The Hyperstone Heist (Genesis): A hack that will change the actor IDs of the colors that some of the Foot Soldiers are assigned to, so some of them will have their correct color palettes:
Switch the actor IDs of the orange & purple Foot Soldiers around.
Give the Foot Soldier that uses the hand shields the pink palette.
Give the Foot Soldier that shoots fire out of his mouth the unused green palette.
Pro Wrestling (NES): A sprite hack that will change all the wrestlers to their real life counterparts:
Fighter Hayabusa - Antonio Inoki
Star Man - Mil Mascaras
Kin Corn Karn - Killer Khan
Giant Panther - Hulk Hogan
The Amazon - Bruiser Brody
King Slender - Ric Flair
The Great Puma - Tiger Mask