FOSS gamedev and creative worlds

What mod should i do?

List of Mods I'm doing within the next 2 months
1.Robot Servant
2.
3.

Do a time-travelling mod. First, it should record all entities' movements and block changes. Then, if a chat command is executed, that mod shall do a global rollback and create entities that were at a time player wants to travel to (mod should create entity for the player too). After that it should unrollback world in real time.

If that's too hard, I would suggest doing Robot Servent Mod.

That would be cool. I will take that into Consideration and if you go back you can see wild spawning entities from my prehistoric life mod.I might make it so you have to use a time portal though.

Would there be your previous self? I just thought it would be funny to see hundreds of time-reversed copies of yourself.

Btw, here is an example of what I am speaking: http://www.freewebarcade.com/game/chronotron/