An idea I have: A first person RPG game in the same style as the first two Elder Scrolls games, Arx Fatalis, and the King's field series (Everything is from a first person perspective, attack damage is based off stamina bar so a full bar means full attack damage minus whatever your opponent's defense rating would be, same could be said for magic regarding a magic charge bar, you can create the face of your character whose face you could see when doing actions like sleeping). It would have the same sort of actions in Gothic in terms doing pointless things like playing a lute or doing something useful like forging a sword. Said story is just going through a region within an island country where the player is trying to make something out of their own life. After beating the game, the player can just do whatever they want within the region.
Another idea I have: Make a story where the player seeks to fight fate with the help of a powerful, thinking it's just a linear path that is evil (think of fate as a rope) but as the player goes forward, things aren't as they seem. Eventually, trying to actually destroy fate is basically like being a small ant trying to destroy a truck. Fate is undying, being a part of the universe and the player finds out that fate is more like a tree, having many roots, than a rope. The point of this game was to make humanity be more of like an insect in the grand scale of things, thinking it's mighty when in reality, it's just another animal within the universal wilderness but even though fate is an adversary that can't be destroyed doesn't mean the player must despair but instead should brace against the wave and try to stand through it.
Another idea I have though it's more of an animation using machinima: Ultimate Muscle Roller Legend using a couple characters I made from two games (Dark Souls and Skyrim) trying to chase down Rainbow Dash. Don't ask, it's not suppose to make any sense.
Final idea: A SMT fan-game where Jesus is a character who is on the side of Neutrality ( This is due to how Jesus says things like treat your neighbor like how you want to be treated.) The Law hero would make the Law side actually be sympathetic as would the Chaos hero. Good and bad would have an effect like Law and Chaos in terms of ending (example: Chaotic good player fights in a darwinistic world for his clan, chaotic evil is a bloodthirsty pack leader who would eat even the weakest member, Lawful evil would be harsh in judgement to all while Lawful good is more accepting to his allies. I'm sure this isn't clear and I wouldn't blame anyone since really, this isn't thought out well.) The story is that demons come into this island city through a portal (Doom reference FTW), and it leads to a clash between Law and Chaos. Jesus gets in the mix, wanting to prevent Chaos from destroying civilization while also wanting to stop Law from making a paradise that has no genuine love for God, not to mention this would lead to the deaths of many and what not. Player chooses their path by mid-point in the game, siding with whatever side they believe is the best. Siding with Jesus and the neutrals means fighting both Law and Chaos while siding with either Law or Chaos means getting rid of Jesus since Jesus leads the neutrals against both sides.