Would you like to see a new, even harder difficulty mode in future KH games? 

I don't think so. We already have four, and if you count a Critical lvl1, you have five, and it goes from easy to super hard with these modes.

So I'd say we're good with the ones we have so far. I have no ideas for new modes as well

Insane difficulty

but honestly I think crit level 1 is good as is for the hardest difficulty. 

I don't even waste my time with Critical. So no.

Not a bad idea. But it would be useless for me.

If there was a harder difficulty than lvl 1 Critical, literally no one would be able to beat it.

would be cool seeing one like heaven or hell from DMC when every attack (you and enemies except bosses) is a one hit kill and the game would make it so there are no unblockable/undodgable attacks...it will be so that the animations and sounds will help you time the evasion.

Critical'er