"is it possible to have more then one composer.json file per repo."
No.
You can't register the components separately, they will be registered as one big dependency and you will have to import them all into other projects, rather than being able to pull them individually.
However you can register where each component lives in the directory structure so that the autoloader is able to load them correctly.
"autoload": {
"psr-0": {
"Intahwebz\\Component1": "src/Component1",
"Intahwebz\\Component2": "src/Intahwebz/Component2",
"Intahwebz": "src/"
}
}
After including the Composer generated autoloader, creating a new class of type Intahwebz\Component1\TestClass will find it in the correct directory.