Mass editing with Notepad++ breaks file format.
No shit.
Ruby marshal format for strings includes their length (in bytes).
While loading rvdata into ruby is pretty simple, what you want is quite the opposite.
I kind of doubt such tool exists (short of what RPGMaker Trans can do).
Also, there's no sensible way to write such tool for two main reasons:
- EventCommand: ruby RPGMakers weren't written with translations in mind; one of results is that even if the author didn't try anything particularly creative (most don't, but there are notable outliers), you can only distinguish one of text output commands from any other (graphic, sound, game, etc.) by its command code; events composed of these commands are either CommonEvents or events tied to a map - there's no central "string repository"; and if on top of that the author decided to inject some strings via scripts...ouch
- Japanese: any spacing is purely optional, due to low number of phonemes repetitions are more than common, if the wordflow requires it a word usually written in katakana might be written in hiragana and vice-versa; any tool more sophisticated than naive hamfisted search-and-replace would be (more often than not) drowning in false positives
- a mix of the two above: the engine has no builtin line-braking logic - each string has line breaks inserted by the author, so a translator needs to recheck everything by themselves
On the other hand, though, if it's only something like translating interface it shouldn't be hard to do and the number of changes should be fairly low.
Even a partial of inventory names *shouldn't* involve much work.
Character names are a different matter: it depends on whether or not the author had the discipline to create an actor for the char and kept referring to actor's name instead of putting the name verbatim - if they had, change would be nearly trivial, if they didn't - each map/common event needs to be rechecked.