The excellent priest I asked about making reparation before one is in the Illuminative State answered me with a wise and simple answer.
Two parts: one, yes one can make reparation while not through the purification process, such as when one is in the Dark Night, but it depends for what the reparation is being made...and I add that most likely, reparation before purification is mostly for our own sins rather than for other people or situations. One could not, for example, make reparation for serious situations beyond the merit one has gained through the early stages of one's own purification.
Two: the reparation made before the Illuminative State is less efficacious, and the example the priest gave me is the comparison between imperfect and perfect contrition.
If one is sorry for sins because one does not want to go to hell, or purgatory, that motivation does constitute contrition but imperfectly done. Perfect contrition is the sorrow for sin because one has offended God and because one loves God and is sorry out of love, not fear. Likewise, reparation done in the Dark Night is imperfect, as one is still imperfect.
Therefore, for one to make the most efficacious reparation for the sins of others or in intercessory prayer, one must be in the Illuminative or Unitive State.
These facts add to the impetus to allow God to purify one.