Thanks Phi that sounds great
For my first point i basically just mean in the JSON you would add some code to add a edittime button that appears in the properties (which sounds like the current plan), however when pressed it would then launch a EXE you had in a Data\Runtime extension folder or some other MMF2 folder which the SDK would be able to find.
I am not sure how you will be doing the GUI controls in the JSON code but with a quick guess for the button to run a exe you could maybe have something like this -
"Editor Properties":
[
[0, 'Value Input' , 'Name:Test 001', 'Min:0', 'Max:100', 'Default:0'] // Some other control
[1, 'Value Input' , 'Name:Test 001', 'Min:0', 'Max:100', 'Default:0'] // Some other control
[2, 'Button' , 'Name:Run Map Editor', 'OnClick: Load('Data\Runtime\ExtName\MapEditor.exe');'] // The button that loads the EXE you want
]
Then with MapEditor.exe (or any other exe you wanted) you would just use it for whatever you needed like a helper tool, in this case to make a map file that could be saved and loaded with the extension actions etc.
I guess my idea would just be a way of running helper apps that would normally be external tools but if you added in a way for extensions to load properties from files also they could get saved data back also and work together as if the EXE was a dialog from the extensions properties.
With my second suggestion i mentioned a external TXT/INI file based preset system which would be great but another useful thing you could do with the EXE launching would be to directly manage those TXT/INI files to add.remove a preset etc. It sounds like you wanted Multi-linguistic INI's so i guess you could do basically the same thing same again with that and launch a EXE tool to directly manage them also.