Personally I think this is useless feature and should be removed completely, as it just adds additional problems for both Host and the Server as this file should as well be in the directory for addons to work.
Most of addons are binarized upon release and cannot be changed by third party folks anyway...
Why restricting it via some other ways?
I think reading this explains it all : https://community.bistudio.com/wiki/ArmA:_Addon_Signatures
Bikey's are there to stop hackers, as it allows server admins to restrict what addons can be used on there server. This can be disabled by setting | verifySignatures = 0| and then all mods are allowed.
This causes hardly any problems for the host and is as simply as dropping a key from the addon maker into a folder.