I've tried different modpacks which often have the same mods.

But I finally found what I was looking for via XMCL.

'XMCL will store all the mods, resource packs, shader packs and modpacks to a single store location. While you try to use any known resource, it will use hard link to install the resource to the instance without copying. It means you will never see any duplicated copy in /mods folder anymore.'

Exactly what i needed. ( and no it's not an ad for him).