Lightroom adjustment/cleanup of settings for historically imported pictures

Question

Background:

• I am using Lightroom (newest edition, subscription) for two years, and for the first year, I did not understand enough of the settings, so I imported over time about 80000 photos with different settings - none of them really what I want now, and some of these settings cannot be undone.
• From these photos, about 2000 have been extensively processed and exported/published.
• I have the 'Save processing in XMP files' activated.

What I want to achieve:
I would like to start from scratch, importing all pictures into a new catalog, with the 'right' import settings (I know what I want there now). However, I do not want to lose the 2000 processed pictures' history and processing details.

Possible Approaches:

1. Remove all XMP files except the 2000, create new catalog, import all photos again. That should conserve the settings on the 2000, and allow me to import the rest with my new import settings. However, it might not, and it is a huge effort to manually handle the 2000.
2. Create a new catalog from scratch (lose all history, but keep the old catalog). I can then - for each photo - change between the catalogs see what history there was. Painful, forever.
3. Write a program that handles the XMP files: read, adjust the content to the desired new import settings, write back (skipping the 2000 photos, probably recognizable by size of the XMP). Coding effort, and unsure if it would even work.

I am looking for other approaches, tools, or maybe even functionality in LR that I don't know about yet, to achieve what I want - one catalog with 80000(-2000) photos with my desired import settings, and 2000 with the history as is.

Answer 1

If you have identified the 2000 images that you want to keep intact among your 80 000, the following steps will do the trick:

1. Create a new catalog (if you want/need to);
2. Import the 78 000 images in LR;
3. In LR, select all those images, right-click and then "Develop Settings" > "Reset". Now you have erased all the unwanted changes to those images. The XMP files should be adjusted accordingly;
4. Import the 2000 images, their associated XMP sidecar files will bring the changes you want to keep.