This sounds like a fun idea! If my charas fit for you I'm totaly in ^^
Main Chara Osram: An independent outcast girl, loves to travel and explore, thinks big about herself, doesn't care to tell you the baret truth but is often too direct with words. Is totally in for a fight!
Main Chara Xenon: Scientist from a big city, want's to be left alone, has a rich and successfull mother but hasn't accomplished something himself. Friendly and well-behaved but has a tiny voice in his head that leads to bad stuff.
World: Some sort of fantay thing but without magic, there are ruins of their ancestors with some hightech-relicts they don't jet understand. They don't know about electricity, so most of their stuff is powered by steam or energy-stones from the ancestors. Huge cities with lots of forest and wastelands in between.
Story: Basicly, Osram and Xenon are forced to play a happy and loving couple, so he get's funded again from his mum. I kinda love to draw them learn to get along ^^' Also there are some sinister people with eeevil plans for the city.
Here the story as rev.
For the collab, it migth be a problem if the setting is in a modern place, as they don't know such things. But it also might be interesting if they had to get along with such a situation ^^ Xenon would be amazed about everything and Osram would think about how to sell that stuff. I also could toss in a chara who is from the past (he knows about the modern world) and could help as guidance.