Short answer: YES
Long answer: I'm actually currently writing 2 different stories with this premise. ^^
In the first one, the 'isekai' is actually just a simulation meant for humans to experience as entertainment (basically, a virtual reality). Some of its inhabitants realize this and want out, so they enlist the help of a human to change it. This isekai'd character is a major player in the plot, but she's really just a supporting character; the focus stays on the virtual beings.
In the second story, the 'isekai' is a similar kind of simulation, although those of its inhabitants who DO know they are fake accept this as normal. Certain inhabitants can control and modify the lives of others as 'stories', and the 'isekai'd' character enters the world to ask the MC to make her into a story. In a way, this is almost meta-isekai. XD
So anyway, yeah, she's a little closer to being a main character, but still plays second fiddle to the real MC. She's only present for the middle 2/3rds of the story.
In conclusion, I think it's a very interesting idea, with the potential for lots of different creative takes. ^^ Hopefully more creative than the ones I presented.
...You're right, this would be a challenge. P: But if someone could write it well enough, I would definitely read it. I love good convos; I think lots of authors could benefit from putting their focus on quality dialogue.