Even if this were done, I wonder if most software would understand U+2007 or other non-breaking spaces as spaces for the purpose of full-justification or right-justification and hide them when they would otherwise appear at column right position.
Such usage would be a higher level protocol. The general plain text model for Unicode assumes that any extra space needed for justification is added by the renderer by expanding inter-word and inter-letter spaces.
The various spaces in the 2000 block are intended to be used for the purpose of providing fixed amounts of space, something that's needed for special purposes, such as separating parts of a mathematical formula by a specific amount of space, when the location for the space is floating with the text.
One of the narrow spaces can be used in math for a space that's ordinarily a bit narrow, but can be expanded, if that's needed. See for example the TeXBook for a description of the use of this and the fixed width spaces. ZWSP can be expanded in Thai-style letter spacing.
Other than that, none of the spaces should be construed for special behaviors under justification.
A./
