Creating morphs with magnets in Poser can be a fast solution sometimes.
If you want heavy modifications you're prolly faster in an modeling environment.

I don't know C4D's coffee... Maybe you can add mirroring via a script in C4D.
OTOH, it's hard to believe that C4D does not support mirroring by default coz it is some very common function.

Clothing the character first and then model (or deform) the morphs to it sounds really odd.
It works well with magnets in Poser because you can often apply the deforming on the figure also on the cloth part. That saves you the work of doing it on the cloth from scratch but also requires most often additional deformers for tweaking the cloth.