Currently, InDesign's vertical justification is very basic and has several drawbacks that render it useless for professional layout.
1. Very limited Control. The only parameter you can set is the additional gap that will be added between paragraphs.
2. Beyond that threshold, InDesign adds gaps between the paragraph lines - a typographical catastrophe, without any possibility for control.
3. The VJ control is and text frame attribute and not in the paragraph style level' which causes un proportional separation between headlines and text - again, typographically un expectable.
4. The alignment is done without any consideration to the amount of text in the frame, and needs to be treated (either manually or by script) in text frames that contains a small amount of text, like at the end of a chapter.

The proposed solution will define some new attributes and features to the full VJ, which will improve the result given in the current situation, and provide a solution to the above mentioned problems.

My proposed solution is as follows:

[Paragraph and Paragraph Styles]

Here are two optional methods:
[Method A]
In the Paragraph and Paragraph Styles attributes, create five new fields:
Title: Full VJ optional Spacing
A. Space before: Field 1 - Max. expand. Field 2 - Max. shrink.
B. Space after: Field 3 - Max. expand, Field 4 - max. shrink.
C. Field 5 - Line spacing. The default value will be 0 (zero).
All the values in Millimeters\Points.
When the basic value of the Space Before\After is 0 (zero), fields 2 and 4 will disabled.

[Method B]
In the Paragraph and Paragraph Styles attributes, create a Justification like interface to control the parameters settings for the full VJ options, except the parameters will be: Space Before Variation, Space After Variation, and Line Spacing Variation.
For each parameter, the 3 percentage values will allow setting the Minimum, Desired, and Maximum spacing changes allowed.
The full VJ will be implemented according to combined calculations of all the above settings (Space Before spacing method and values, Space After spacing method and values, and line spacing value), similar to how the 3 parameters 3 values combination of the Justification feature works.

To resolve cases when the Space Above or Space Below are set to 0 (zero), in which the respective 3 value fields of the Space Above Variation or Space Below Variation should be dimmed (because you can't set a variation to a 0 value) ,my suggestion is that this section/dialog will include a representation of the Space Before and Space After fields which will allow the user to set spacing value directly from the full VJ settings interface, the same way the Indent value fields allow to set the paragraph indents from the Bullets & Numbering dialog/section.

In addition, add a Force Justified Vertical Justification options (radio buttons) that will determine the full VJ behavior when the values of all the parameters are not sufficient to achieve a full vertical justification in the current text frame height.
Option will be: (1) Justify to Top; (2) Partial VJ - the result with the maximum values applied; (3) Forced VJ - a forced spread with spacing violations over the defined values.

[Text Frame Options]
Add a Contents Threshold field to the Text Frame Options dialog that will allow the full vertical justification to be performed only if the text frame contents fills more than the designated percentage of the frame height.
The default value should be set to 85% or 90%.