it was my mistake that i approached it the wrong way. its not about the dynamic jacket.  i needed to have shoudler pads under the jacket.

 

so what did i do? i modeled 2 simple shapes for the shoulders. they look similar to the pads under the jacket. then i was thinking, ok how will i now parent this to the body. ohhhhh yeah we have conforming clothes. this is perfect.

 

this is how this looks. those are conforming shoulder pads. the groups are only for the M4 chest. that way they dont bend when you move M4's shoulder.