when playing Arma 3 with mods many of my friends and me (of course other Arma 3 users may also be affected by this issue) suffer from the fact, that many servers are not whitelisting/allowing mods in general.
This leads to the circumstance that you often have to disable really good mods and thus dont use them.
I think, you could really push the modding community of Arma 3 and make this even more popular, if you could offer the possibilty to whitelist "bigger and popular" mods like "JSRS", "Blastcore", etc. to a central database and make them something like "valid community created addons" (for proven and non-dubious modding projects). (IN ADDITION TO THE CURRENT SYSTEM NOT INSTEAD)
This would easify the progress of adding mods to server-setup and thus increase the number of servers, you can enjoy your mods on.
If it isnt wished, it may be turned off.
I guess a "not allowed" option regarding a "proven configuration/mod collection" is better and more usable than an "allowed"-option for each mod, where you needa add every mod separatly and get never in touch with unkown mods.
Server Admins could then differ between this option (and of course disable this if they dont wish players to use them) and the option to allow/forbid smaller/each mod(s) seperatly.
This would offer a great benefit for the usability of mods, make modding more popular and pushes Arma3´s modability even more.
ITS JUST AN EXTENSION OF THE CURRENT SYSTEM NOT A REPLACEMENT.
Another important point for us is that we would love to see the option to check downloaded mods by something like a BattleEye-option to assure there is nothing like a hidden cheat and thus lose our beloved account...
Hope these are serious options for you!