Ahh, yeah that would be an issue I geuss xD.
As for modding RPGM games in general, a normal RPGM MV game, you just need to grab a copy of the "Game.rpgproject" file, and put it in the game's "www" folder, and you can open it in the engine like any other project you made yourself. (And there are similar files, named sligtly different for different version of RPGM games)
If any encryption have been chosen for the game originally... well the encryption is beyond terrible, there are easy to find tools online, that reverts that, in litterally a second or 2, easily.
Technically, you could also edit the json files directly in any text editor, though that would be really hard to do for anything but the smallest/ simple edits ofc.