Mixing is very difficult when you've got instruments all in similar frequency ranges. It's hard to carve clear space because they're stepping all over each other.
I'd also caution against over complicating ... meaning if there's not a solid reason to do it, don't do it. Having clear purpose is paramount. "Just because I can" is never a good enough reason by itself.
Most of what I do is take instruments out unless it's critical for them to be there.
Just random recording thoughts ...