Glad you steered away from repacks...
Unfortunately, the only way to do this is by using scripts. Obviously, you can't just dump tables from DB to another that are completely architected with the differences. The more differences between the table structures, the more work you have to do to manually import each character.
Tips:
do a "desc <TC character table name>;" in mysql client.
then do the same to the repack table. "desc <my repack table>;"
You will have to do that to each table in the characters schema, then modify the differences in your dump (unsafe route). Otherwise, like I said, just a script for each table, import one row of character to all tables that match or have similarities. Then log into that specific character and test it out. if things are broken, or some data is missing, then it was an invalid entry. Try and try again, until the one character looks to be working correctly with all the necessary items. Then you can import all of your other characters.
Good luck!