I saw your readme after posting and managed to find the strings for dialogue, briefing and weapon descriptions.
I am having a tough time finding the strings for the menu items, like options items and Start Mission from the loadout screen. Do you know what file type you had to edit for RS3? I have a bad feeling they are in some .dpd files that on the install.
Thanks for the heads up on them not liking fan translations, I'm sure mine will be vastly inferior to what they have working, I'll have to consider if I want to post it prominently if I do.