This is probably one of the last places that you'd want to(and will) touch, but here it goes anyway:

1) Introduce the concept of groups, this obviously won't affect the behavior of the stack and is mainly a organizational tool that makes reading, working with, and copy/instancing a group of modifiers easier, it also can act as a barrier for selections passed up the stack, ie. the selection would only be propagated throughout that particular group(instead of using a Poly Select to stop it for instance).

2)(And here's the big one, If you didn't like the first one you're going to be furious about this) And that is the concept of copy/merging the stack, let me explain, if you've worked with Photoshop you know that you can put a merged version of your visible stack on top of the stack, all the layers are still there, you just have a representation of the stack up to that point, in other words you have collapsed your stack, up instead of down the stack, ie. a non-destructive collapsing, so back to Max, you could represent this merged layer with a null layer/mod that only stores a vertex/face index and nothing else, when it's created and/or activated it will obscure/disable the stack below it, and when it's deactivated it will propagate the deactivation up the stack to all the layers depended on this layer, this could create a new method of working non-destructively inside of any given object and without the need to create a new copy every time we want to collapse the stack.

The stack and command panel are the heart of Max, and operating on them makes you uncomfortable I realize, but it's been so long and things can always be improved no matter how great they are.

A working viewport space viewport mask similar to Zbrush. While working on this big building file with single poly floor slabs and messy geometry and only needing to build out a small corner office, I was wishing that I had some sort of viewport mask to isolate areas quickly rather than slicing the model or detaching faces to work efficiently. For instance, Z brush can mask out areas to make work flow efficient on THAT specific area only. What if Max had a feature where you could draw a dummy box around an area and work in ONLY that area? That would be helpful in my opinion, but maybe I am dreaming.

Thanks.

Right now we can convert sub-object selections through using shortcuts in modifiers such as 'Edit Poly', but that's a one time operation, what I'm asking for is the ability to actively convert a sub-object selection to another (say a face to vertex selection) and pass that up the stack so when I animate the face selection the vertex conversion is actively propagated up the stack.

The 'Turn to Poly' or 'Poly Select' modifiers seem like suitable places to implement this, there's already a similar functionality implemented in 'Turn to Poly' that actively Inverts a selection, ideally you could add an extra rollout in there with three 'To Face', 'To Edge' and 'To Vertex' radial buttons and an options area that would determine the method of conversion i.e. 'Borders/Outlines', 'Inner Area' or 'Inner+Borders', basically representing the Shift, Ctrl+Shift and Ctrl shortcuts respectively.

An idea, easy and happy!

Example :

1. I have to model a building with 2 floors, and some furniture on each.
I say the first floor plan( with the world coordinate system z = 0 ) make me easy to model some furniture than other ( In this case I mean 2nd floor that z =/= 0 ) because i have easy way to check the height of s.th and lazy to Ctr+N. So It would be happy that I can select the 2nd floor and make it become the z' which z'=0 and all things in the 2nd floor will obey the z'.I mean I can change the world coordinate system to the the world coordinate system tamp and reset it back!

2.I have a box ... in my scene, I want to make a viewport configuration to link with box ...'pivot just 1 click complet by pick ...

It would be happy! sorry for ma bad english!