Restrict DCM stage movement based on reason and access rights.

We have implemented custom section for opportunity similar to OOTB with DCM. The stage movement is restricted to few users as per acess rights. 

1. The stage movement happens on click and should be allowed only when reason is provided which is captured as detail through pre-config page in business process
2. if it s cancelled it is reverted back to previous stage.

(Business process is called when on change of value in DCM stage look up happens- through js code in edit page)

Right now it is allowing users without edit access to edit the DCM though insuffient permissions error shows up.

Can someone guide me implementing the same or suggest any alternate approach?

Also let us know if this stage  movement can de denied to other valid users unless the current user initiates movement and gives reason or cancels it.

Thanks,

Gokul