By the time you are 'compatible' then you have implemented everything needed to also be a 'drop-in' but data file formats might need a conversion.
So convert from Minecraft data files to Pumpkin data files. Then it could drop in.
Even if they supply a tool, isn't it drop-in.
Otherwise I'd so no software in existence is really drop-in. Most of them have some update that has to happen.
By the time you are 'compatible' then you have implemented everything needed to also be a 'drop-in' but data file formats might need a conversion.
So convert from Minecraft data files to Pumpkin data files. Then it could drop in.