I am working on a mod project to allow xnb mods to override existing locations without needing to replace xnb files. This same mod is also intended to allow for new locations to be added easily, or for tiles in existing locations to be edited without needing to replace the whole map. Below is a link to a example of the intented json file structure to make all this possible: https://github.com/Entoarox/Stardew-SMAPI-mods/blob/master/manifest-example.json What I am asking is for map editors to take a look at it, and suggest any ways that this could be improved/added upon. If you have questions ask them, I will answer them ASAP.
I am afraid that we are actually going at the same problem from two very different angles, but when it comes to modifying a location that is much easier to use, when it comes to adding or replacing them, my mod would be better simply because it is actually adding the maps in question directly into the game, not patching existing ones Perhaps one day this mod wont be needed anymore, but for now I'm developing it as a stopgap until complex mods like that are capable of doing everything map-makers can imagine without issues
I wish I had something more constructive to add, but I'm not fluent in java. That said, I'm all for a better way to go about map editing. If I understand the manifest format you linked it seems pretty well organized, but never having done this before that's all can say. Good luck!
First beta version currently being tested out by a select group, interested map makers can ask for a invite to the beta testing group
Feature creep is the bane of all existence, So to make it so ALL is released eventually, I have forced myself to stop the creep and get 1.0 released before any more features are added Hopefully I can finish off the current beta in a build or two, and everyone will get to enjoy the magic that is ALL