When you connect to a server with mods, the Minecraft Forge starts downloading the mods (will work better with the mods folder) and installing then. (I recommend put the mods in a separated folder with the name that have in configurations of the server, ex:

server.properties:

mods-folder-nameid: ForgeServer

 

And the mods folder that the player will download will be named as ForgeServer, the mods will be downloaded there. [Auto Detect Conflict if have a server that use this folder Name/ID])

 

If the player left the server, the mods will removed (not deleted), and can play singleplayer without mods, can play other server with mods (downloading automatically the mods), can play singleplayer with their mods...

 

Explaining more:

If you want to add mods to the server, put on the "mods-folder-nameid" that have in your server location.

The mods-folder-nameid will be the folder that:

The player will download the folder automatically.

The player will download the mods in this folder automatically.

The folder only will work with the server that have the folder name in "mods-folder-nameid"

 

 

Sorry for my english.

 

With this auto download, the mods server will appear everywhere.

 

(Idea by MTA [Multi Theft Auto, a Grand Theft Auto: San Andreas mod multiplayer])

That would require relaunching the client when you connect to the server.

Requested many times, all denied.