Vertex Group stack for modifiers

I've been thinking of the best way to do parametric selection of vertices for use in modifiers such as bevel. This proposal has two separate concepts:

1. Ability to assign vertex groups from modifiers such as Boolean
2. The concept of an implicit vertex group stack

Concept 1 is something which I feel would be nice to have regardless of whether or not 2 gets implemented. The ability to assign for example, the vertices along the intersection to a vertex group (potentially with different modes such as add, replace, invert to change how it would be mixed with the existing state of the vertex group) when doing a boolean operation would allow you to then later use those vertex groups to control other things such as bevel modifiers.

Concept 2 is a nicer way of interacting with these generated vertex groups, and would likely make them used more often. It is the idea of having a list of vertex groups that is added to and taken from by modifiers. I will use the 'boolean then bevel' idea again as that is quite common. The Boolean modifier would push a vertex group which contains the vertices along the border of the intersection to the stack. The following bevel modifier would then be able to 'consume' this vertex group as the selection for what to bevel. This saves cluttering the vertex group lists with lots of groups which were only used temporarily, and saves the user from having to manually create and name every one.

The idea of the stack is so that modifiers could progressively add to the stack of vertex groups, then a modifier could pull off the last x groups and do something with them. This greatly simplifies the process of parametric modelling in a similar way to how Houdini does selections.

Solidify could assign either the front or back face vertices to the stack.

Boolean could assign either the boundary or 'intersecting' vertices to assign to the stack.

A new modifier called 'select vertices' could also be added to only add vertices which fit a category (such as sufficient angle, face size, border vertices etc) to the vertex group stack without modifying the mesh.