well i think you see mods very shallow. mods are love! mods are freedom! mods are justice!

no jokes aside, if you look what mods can add to a game it is amazing. new dialogue lines, new events, if one have the pictures even complete new scenarios. modding is a godlike art!
That's the thing tho, the way the illustrations are rigged will make the job far more complicated, especially implementing new scenes since you'd need to change plenty of said illustrations and unless you're a good illustrator that can actually replicate other people's artstyle, it's gonna look weird mishmashing both styles or end up looking as bad photoshop.
Granted I'm not saying it isn't possible to do, but the work to do so would be far more than someone making a fan game of The Manor from scratch, especially since most stuff (besides character sprites) are basic items already in the RPGMaker library. The easiest thing would definetly be text as you could replace the existing one in similar fashion to the Urban Demons' Xalenda mod, that makes the "Corrupt" part a bit meaner in dialogue.
There's potential indeed, but more often than not, mod support is heavily limited by the engine and availability of info of the game's files. Again, not that it can't be done but rather that more complex stuff (events, new scenes, etc.) would be far easier and quicker to do by making a fan game from scratch.