I think a point and click Sliders game back in the 90's would have been good.
Something like the Broken Sword Series or the Discworld Games.
Kind of a Detective style thing. Find Clues, talk to People etc to solve a Crisis on a Given World or find your fellow Sliders if split up?
I think a Detective type approach could work in a Modded Game or Sandbox type Game now too but not point and click.... Although I have heard of some open source software which people are using to make Custom/Home Brew Visual Novel and Point and Click Games as Indie Projects.
A Modern Point and Click I saw recently was Archangel: Martian Orbit.
http://www.youtube.com/watch?v=u4UYrF5y … ata_player
I agree with your idea of a changing Town/City Slider_Quinn21, that sounds pretty good. I saw a GTA: San Andreas Mod once where the Modder raised the Sea Level in the Game Engine and Flooded everything. Seeing San Fierro like that reminded me of the Early Season Sliders Ep with Flooded San Francisco and that Shop with a Mural of a Drowning Moon. 
A very easy Mod Tweak but it completely changed the City's feel and look so yeah minor tweaks for big impact are possible and bigger changes like Clothing Style or a Nudist World lol are easyish too! Architectural changes may be more fiddly but designing buildings as frames with changable skins like for an NPC might be doable to hot swap Architectural Styles? Changing City Layouts and Grids maybe too?
A game which did explore changes of a Town even if only in a minor way was Shadow of Memories/Shadow of Destiny due to seeing different Eras of the same Town but the Architecture was mostly Static with only Minor Changes.... Effective though anyway.
Not so keen on the Kromagg Arc taking over though.
Invasion type maybe or a random event/threat maybe?
This discussion has made me a little more optimistic that some kind of Mod or Indie Game may be possible! 
"It's only a matter of time. Were I in your shoes, I would spend my last earthly hours enjoying the world. Of course, if you wish, you can spend them fighting for a lost cause.... But you know that you've lost." -Kane-
