I, and most likely others as well, either don't know how to install mods, or have general trouble with them(for example, I have tried every process and every idea given to me and have still not been able to get a mod loaded.). I think that this could be made easier if the game was made so mods could be installed as easily as resource packs. This new feature could make it easy for players to be able to install their favorite mods and turn them on and off while creating a new world or from the title screen. Also, on hardcore mode, mods could be automatically shut off to keep the game a challenge. If the player travels to a server, the server would be able to turn off the unwanted mods easily. Minecraft is a game with no limits. Let's make it easier to to that.
Yes, the entire Mod API will make Resource Packs be mods, in addition to textures, sounds, etc. This suggestion is already being implemented.
EDIT: In fact, the mods you can't get to work probably use Forge or ModLoader, with are third-party "API"s that aren't as good as the upcoming Mojang one (based on the progress so far). Otherwise, all you need to do is add the given .class files and/or folders/textures, and delete META-INF. It's not that hard.