For a long time I've been trying to come up with a good conceit for a free-travel time travel RPG. That is, a game where the players can roam to any time period they please freely, rather than being shuttled through time on a plot ferry.
The problem is that time travel pretty much takes care of all the human
concerns that tend to drive us. Even the biggest challenges can be
solved by simply popping back to before they started and changing a
small variable. A time traveler who wants to keep his family from dying?
Huge plot line! But the only way to make it difficult to do that is to
add arbitrary levels of complexity and turn it into a fetch-quest thing
where you have to first go back in time to change the things that are
stopping you from changing the thing you want to change. It's not very
compelling! It's just complicated and pointless.
So you introduce overarching time demon plot lines where in the end you
have to fight against time itself or your older selves or some other
stupid thing that is forced down your throat. Your personal goals have
nothing to do with it - you have no interest in this plot except in that
you can't escape it!
How do you introduce human interest into a story inherently about someone who has no human concerns? Even if they have human impulses - say, they love somebody - they can still just pop off to fix whatever might go wrong. The only game I can build out of that is time-traveling whack-a-mole.
Which, actually, sounds kind of interesting. BUT! Let's presume we want something with a bit more depth.
How about this? Time travel as self-improvement.
There are a lot of time travel games about restoring the timeline to your normal timeline.
Shouldn't it be the opposite?
Wouldn't a time travel go back in time and tweak it so his family was rich? So he was born with superpowers? So he was elected president?
You could even ally with other time travelers, cooperate to improve eachother's time lines, to use less of your life tweaking your timeline so you have more of your life to spend on other stuff...
"Hey, let's all just have the same parents. And back in the fifties, we can give them the mutant gene..."