Multiple controllers per page + Multiple instances of the same model

Thanks for your answer!

I'm not saying that CodeIgniter restricts me - I'm trying to figure out the "best practice", aka how such a problem is usually solved while making good use of CodeIgniter's features and having a nicely structured code.
Basically, for (4) I thought of having additional actions that will be targeted by my client side javascript code. This idea seems ugly to me, though.

Thank you for the link! I think I get how they solve most of my problems. Although, it looks like I would have to load the additional controller/view from within another view - Wouldn't this be considered as a little "ugly"? In my head, I map "loading" to "logic", but the whole point of MVC is to render the visual part independent from the logic part, right? (I could be totally wrong, and probably am, but right now this is how I think of it - It would be really nice if you could maybe elaborate a little bit so I can grasp everything a little better.)
(Oh, and I also don't get how that addon would solve my "problem 2"?)

Thank you very much!