Correct, Battlebelk's tool will make a new replacement core.lvl for the entire game.
The correct place to put it is at the very top of the file, before ScriptInit, in a new function called "ScriptPreInit". ScriptPreInit is a special function that was known about in BF2 but after some digging through the binary, it was determined that ScriptPreInit is also a valid function that is designed to be loaded before the main game files. So what happens is ScriptPreInit is in your mission, it loads, and that coreaddition.lvl is loaded first. The game then goes and loads all the normal stuff it uses (core/common/etc). The base game behavior is that if an exact localization entry is found, just skip over it. So normally you would not be able to overwrite the main game's core.lvl since it loads first. PreInit can get you in before that and allow you to make "Rebel Soldier" into "Rebel Scum" using a much smaller addon file than replacing the main core.lvl.
Back to the question, yes, the way I have it structured is that it would go in the "NEW" folder in _LVL_PC, that is correct.
Finally, yep, you can just use BFBuilder's localization tools and the core.lvl generated from that to put in this "NEW" folder.
Let me know if you have any more questions
The correct place to put it is at the very top of the file, before ScriptInit, in a new function called "ScriptPreInit". ScriptPreInit is a special function that was known about in BF2 but after some digging through the binary, it was determined that ScriptPreInit is also a valid function that is designed to be loaded before the main game files. So what happens is ScriptPreInit is in your mission, it loads, and that coreaddition.lvl is loaded first. The game then goes and loads all the normal stuff it uses (core/common/etc). The base game behavior is that if an exact localization entry is found, just skip over it. So normally you would not be able to overwrite the main game's core.lvl since it loads first. PreInit can get you in before that and allow you to make "Rebel Soldier" into "Rebel Scum" using a much smaller addon file than replacing the main core.lvl.
Back to the question, yes, the way I have it structured is that it would go in the "NEW" folder in _LVL_PC, that is correct.
Finally, yep, you can just use BFBuilder's localization tools and the core.lvl generated from that to put in this "NEW" folder.
Let me know if you have any more questions