I want to do such things to. That's why I'm going into computer courses about programming and stuff.
I tried out a program called "RPG maker 2000", the best in my opinion throughout the RPG maker series. You could design your own rpg pretty much like the old FF games, monsters, abilities, equipment, animations, characters, music, everything. All you needed to do all that is being good at drawing stuff such as tiles or parts of animations to create a new sets instead of the original set you got in the beginning.