So couldn't we say that a just society be one in which people were respecting one another's capacity to choose--beginning with choosing whether/how/to what extent to be involved in any way whenever any choice is being effected (actions are being taken to bring a choice to fruition)? Including in that not only actions involved in effecting a choice, but also the affects of choices on others, that would seem to boil down to a handful of restrictions to maximize freedom: no killing, harming, coercing, stealing, or manipulating (lying, cheating, etc.) in effecting any choice--to include all choices involved in the economy and the political process, both of which are nothing but effecting choices. In short, the 'ethic of justice' would be 'mutual respect in effecting choices'.

All that is left for a fully just society is to apply that ethic to the structure and functioning of the political and economic systems of a society. Since a democratic political system already accomplishes that, all that is left is to apply that ethic to the economic system.