Now that we are facing great changes with Minecraft and Forge, i would like to suggest changes in the modloader system.
For example: Would be possible to organize mods in two groups named client-mods and content-mods?
The client-mods would be loaded with the client load itself, but, the content-mods would be loaded upon connecting to a server (a online server or the local one used by singleplayer). Also, the content-mods's config would be stored in per-server folders.
This way, your mod's config used in singleplayer wouldn't be replaced if you want to play in a online modded server.
See ya!
P.D: Obviously, mod developers would need to set in the mcinfo file a new field, indicating if the mod is a client mod or a content mod.
By default, every mod without this metadata would be recognized as a client-mod.