I remember in one of Contextcapture example videos there was an workflow how to add additional photos to improve details without need to reprocess all. Can't find it anymore.
Perhaps this will help:
https://communities.bentley.com/products/3d_imaging_and_point_cloud_software/w/wiki/30215/managing-partial-updates-on-large-contextcapture-projects
https://communities.bentley.com/products/3d_imaging_and_point_cloud_software/w/wiki/41654/how-to-merge-models-from-different-data-sources
You should just have to create an additional block and merge it with the initial production.