What I would do, and I'm sure there is an easier way, is to go into your database before the patch and save your items, objects, characters, accounts, etc. (whatever you want to save), Save them as .SQL files. Then when you get a new repack for your updated patch, run each saved .SQL files and use the "continue on errors" function, I know navicat has one, im not sure about others since I dont use them. But this should add all the custom content you created, and then ignore all of the things already in the game.
NOTE: THIS WILL ONLY WORK IF YOUR NEW REPACK IS THE SAME TYPE AS YOUR OLD ONE. EXAMPLE: Ascent/Mangos (If not you will get errors because your tables will not match, say something doesn't exist or is missing.)
If there is an easier way than this, or I said something wrong that wouldn't work please correct me and suggest a better way

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I am giving this information from personal experience when my friend quit and gave his server for me to run for our other friends. I needed a new repack for an updated patch, but my other friend had spent all summer making custom content, and didn't want all that time to have been a waste. I successfully did this, kept all custom content they created, and had the new content from the repack.