Security is fine and all that, but can you please apply the limitation only to clients by default or add a parameter for both client and server to allow both directory writing and unlimited filesize. There are existing workshop mods and mods in development that require this, and the server owner should be able to "accept the risk" or having files written to the two dirs when he wants to run the mods.

I saw you changed the file size to 5MB now, but mods that save more than just a bit of data require much more. The rail node system for the chernarus map is 30,1 MB, and I will certainly not split things into pieces that belong together just to bypass the limit.
Without a parameter like "-AllowLargeFiles" something like my train mod is doomed, because I can not write my in-game data to disk for distribution in the mod files. It will also kill the community offline mode where people save their custom buildings and any other existing mod that saves data outside of the hive.
You can see such a file attached