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It should be the suhosin.post.max_vars 200 200, that need a bigger value.
If you can estimate how many permissions can be changed and how many not, you will know the minimum factor.
You speak of a local and public setting, but I assume the local is when you run the browser on the server itself and that may not an option for you, is it?
That would allow to leave the public setting to a safer lower value.
But you are on a collision course to hit that wall again.
The only long term solution will be that the permissions can be set more divised (in stead of all items for all groups, all items per group or all groups per item), but that requires a program changement.