Sure, go ahead
Everyone is able to change and add to the Wiki. Just build a proper sub-menu entry there at the translations file so one is able to find it within the navigation at the top.
Just for clarification: You can AND SHOULD also use GetString(SI_constant) within your own created translation file so you do not need to re-invent the wheel and translate already provided ZOs translations. So you are always good in mixing your own localization approach via my described tables, a library, the ZO_CreateStringId(MYADDON_TRANSLATION_NAME1), or any other approach.
But keep in mind that if your addon does not need to show translated texts of different languages at the same time, but only the current client language, you should not load ALL language tables each time, so use the txt file of your addon and specify the different languages in seperated de.lua, fr.lua, ru.ua, en.lua -> only ALWAYS load one of the files as fallback (e.g. en.lua) first and then use $(language) constant to load the client language translation file afterwards.